Partition mobility for partitions with extended code

ABSTRACT

A partition mobility facility in which a partition that is executing one or more applications that have optimized code with one or more extended features is to be moved from a source system to a target system. If the target system does not support the extended mode features, then action is taken to remove the code having those features to facilitate migration.

BACKGROUND

One or more aspects relate, in general, to processing within a computingenvironment, and in particular, to managing such processing.

Opportunities to improve the operation of computer systems are providedby a number of code rewriting techniques. For example, code rewritingmay be used to modify binaries to avoid known hardware errors. In otherexamples, existing code may be modified to improve performance byre-optimizing hot regions, either from binary code, or from additionalinternal representation formats stored by the static compiler that allowcode to be re-optimized without decompiling the binary code.

Various offline optimizers have been used to rewrite code. Theseoptimizers modify the actual binary, making self-referential programs,including those that compute checksums of their own code to validatecorrectness, fail. These offline optimizers also depend on obtainingworkload statistics.

Other optimization techniques, such as dynamic code optimization, alsorewrite code. These techniques, however, recompile code dynamically andstore the newly generated code in its entirety in locations differentfrom the original code to preserve such self-referential behavior.

SUMMARY

Shortcomings of the prior art are overcome and advantages are providedthrough the provision of a computer program product for managingmigration of partitions. The computer program product includes acomputer readable storage medium readable by a processing circuit andstoring instructions for execution by the processing circuit forperforming a method. The method includes, for instance, obtaining, by anoptimizer executing in a processor, an indication that a partitionexecuting an application using one or more extended mode features is tobe migrated to a system in which at least one extended mode feature ofthe one or more extended features is unsupported; and removing, based onobtaining the indication, at least a portion of code of the applicationto facilitate migration of the partition to the system in which at leastone extended mode feature is unsupported.

Methods and systems relating to one or more embodiments are alsodescribed and claimed herein. Further, services relating to one or moreembodiments are also described and may be claimed herein.

Additional features and advantages are realized. Other embodiments andaspects are described in detail herein and are considered a part of theclaimed invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects are particularly pointed out and distinctly claimedas examples in the claims at the conclusion of the specification. Theforegoing and other objects, features, and advantages are apparent fromthe following detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 depicts one example of a computing environment to incorporate anduse one or more aspects of a partition mobility facility;

FIG. 2A depicts another example of a computing environment toincorporate and use one or more aspects of a partition mobilityfacility;

FIG. 2B depicts one example of a plurality of machines having one ormore partitions executing thereon;

FIG. 3A depicts yet another example of a computing environment toincorporate and use one or more aspects of a partition mobilityfacility;

FIG. 3B depicts further details of the memory of FIG. 3A;

FIG. 4 depicts one example of a computing environment including patchedapplication code;

FIG. 5 illustrates an example of a high-level view of a virtual memorymapped to a physical memory using a hash page table technique;

FIG. 6 depicts one example in which one effective address is able to betranslated to different physical addresses;

FIG. 7 depicts one embodiment of an address translation process;

FIG. 8 depicts one embodiment of logic to translate an effective addressto a virtual address;

FIG. 9 pictorially depicts one embodiment of translating an effectiveaddress to a virtual address;

FIG. 10 depicts one example of a hash page table translation structure;

FIG. 11 depicts one example of an effective address being translated toseparate physical addresses;

FIG. 12 depicts examples of translating effective addresses to physicaladdresses;

FIG. 13A depicts one example of a control register;

FIG. 13B depicts one example of a machine state register;

FIG. 13C depicts one example of an entry of an address translationstructure;

FIG. 13D depicts one example of a page table entry;

FIG. 13E depicts one example of a storage key;

FIG. 13F depicts one example of a single extended mode control in a pagetable entry and multiple individual extended mode controls in a controlregister;

FIG. 14A depicts one embodiment of logic to create optimized code;

FIG. 14B depicts another embodiment of logic to create optimized codethat enables extended mode features;

FIG. 15 depicts one embodiment of using optimized code that takesadvantage of extended mode features;

FIG. 16A depicts one example format of a move from machine stateregister (mfmsr) instruction;

FIG. 16B depicts one example format of a move to machine state register(mtmsr) instruction;

FIG. 17 depicts one embodiment of logic to obtain access to and registeruse of extended mode features;

FIG. 18 depicts one example of generated code using extended modefeatures;

FIGS. 19A-19C depict examples of generated code with mobilityconstraints;

FIG. 20 depicts one embodiment of logic to prepare to migrate apartition;

FIG. 21 depicts one embodiment of logic to notify an optimizer toprepare to migrate a partition;

FIG. 22 depicts one embodiment of logic to modify code to migrate apartition;

FIG. 23 depicts another embodiment of logic to modify code to migrate apartition;

FIG. 24 depicts one example of generated code and acceptable cutoverpoints to unoptimized code;

FIG. 25 depicts one embodiment of a computer program product;

FIG. 26 depicts one embodiment of a host computer system;

FIG. 27 depicts a further example of a computer system;

FIG. 28 depicts another example of a computer system comprising acomputer network;

FIG. 29 depicts one embodiment of various elements of a computer system;

FIG. 30A depicts one embodiment of the execution unit of the computersystem of FIG. 29;

FIG. 30B depicts one embodiment of the branch unit of the computersystem of FIG. 29;

FIG. 30C depicts one embodiment of the load/store unit of the computersystem of FIG. 29;

FIG. 31 depicts one embodiment of an emulated host computer system;

FIG. 32 depicts one embodiment of a cloud computing node;

FIG. 33 depicts on embodiment of a cloud computing environment; and

FIG. 34 depicts one example of abstraction model layers.

DETAILED DESCRIPTION

Dynamic code optimization (DCO) offers significant opportunities toimprove the operation of computer systems. For example, existing codecan be modified to improve performance by re-optimizing hot regions,either from binary code, or from additional internal representationformats stored by the static compiler that allows a re-optimizationcomponent to re-optimize code without decompiling the binary code. Asother examples, dynamic code optimization may be used to avoid or fixerrors, enhance security, provide additional features, etc.

With dynamic code optimization, in accordance with one or more aspects,one or more portions of application code are modified (e.g., changed,revised, enhanced, updated, optimized, etc.), and therefore, theapplication code is considered patched (i.e., existing code is usedalong with the modifications). A portion of the code to be modified iscopied, modified, and stored in one or more memory regions (e.g., pagesof memory) that are separate from the memory regions storing thepre-existing or unmodified application code.

When code is patched, in accordance with one or more aspects, separateaddress translation is provided, which depends, for instance, on whetherthe translation is for an instruction fetch or a data access. Forinstance, data accesses (e.g., address translation for data accesses)are directed to the unmodified code (i.e., one or more first memoryregions), while code translation (e.g., address translation forinstruction fetches) is directed to the modified code (i.e., one or moresecond memory regions). Additionally, instruction fetches and dataaccesses for code of the application that has not been copied aredirected to the same pre-existing code, which are also stored in the oneor more first memory regions, in this example. This separate addresstranslation is accomplished by, for instance, hardware support thatselectively manages separate instruction and data translation within aprocessor, enabling only portions (e.g., modified portions) of the codeto be duplicated rather than the entire code.

In accordance with one or more aspects, dynamic code optimization offersan opportunity to exploit additional features or execution modes(referred to herein as extended mode features) offered by a machine andnot otherwise available, known or used by applications (a.k.a.,programs, application programs, etc.) executing on the machine. Forinstance, an application program is developed with a common instructionset architecture (ISA) across multiple generations. Thus, when aspecific implementation/micro-architecture offers specific opportunitiesfor optimization, these capabilities are often not made available in theISA because of compatibility considerations. Even when new features aremade available as part of the ISA, the application often uses a backlevel version of the ISA.

However, in accordance with one or more aspects, dynamic codeoptimization may be used to exploit these additional features that wereotherwise unavailable, unknown and not used by applications executing onthe machine. This is accomplished while preventing other applicationsfrom exploiting an ISA level to which it should not have access. Inparticular, in accordance with one aspect, higher or extended levels offunction are made available to application code generated by a DCOcomponent and executing with normal application level privilege, butother applications are prevented from executing such instructions.

In accordance with a further aspect, an application that includesoptimized code having one or more extended mode features may beexecuting within a partition that is to be migrated to another host(e.g., another machine, system, etc.). When this occurs, a capability isprovided to ensure that the host to which the partition is movingsupports the extended mode features; otherwise, steps are taken toremove those features before migration to the new host. This is referredto herein as a partition mobility facility, which is described infurther detail below.

Computing environments of different architectures may incorporate anduse one or more aspects of the dynamic code optimization capability,including the partition mobility facility, provided herein. Forinstance, environments based on the PowerPC architecture, also referredto as Power ISA, offered by International Business Machines Corporation(IBM®) and described in Power ISA™ Version 2.07, May 3, 2013, herebyincorporated by reference herein in its entirety, may include one ormore aspects, as well as computing environments of other architectures,such as the z/Architecture, offered by International Business MachinesCorporation, and described in z/Architecture—Principles of Operation,Publication No. SA22-7932-09, 10th Edition, September 2012, which ishereby incorporated by reference herein in its entirety.

POWER, POWER ARCHITECTURE, POWERPC, Z/ARCHITECTURE, IBM, AIX, POWERVM,Z/OS and Z/VM (referenced herein) are registered trademarks ofInternational Business Machines Corporation, Armonk, N.Y. Other namesused herein may be registered trademarks, trademarks or product names ofInternational Business Machines Corporation or other companies.

One example of a computing environment to incorporate and use one ormore aspects of the dynamic code optimization capability, including thepartition mobility facility, is described with reference to FIG. 1. Inone example, a computing environment 100 includes a processor (centralprocessing unit—CPU) 102 that includes at least one memory managementunit (MMU) 104, one or more address translation structures 105, and oneor more caches 106. Processor 102 is communicatively coupled to a memoryportion 108 and to an input/output (I/O) subsystem 112. Memory portion108 includes, for instance, one or more caches 110 and a dynamic codeoptimizer (DCO) 111, which may be used to optimize applicationsexecuting within the processor. I/O subsystem 112 is communicativelycoupled to external I/O devices 114 that may include, for example, datainput devices, sensors and/or output devices, such as displays.

Memory management unit 104 is used in managing memory portion 108including facilitating access to the memory by providing addresstranslation. To improve address translation, the memory management unitutilizes one or more address translation structures 105 including, forinstance, a translation lookaside buffer (TLB) and a segment lookasidebuffer (SLB) which, in one embodiment, are located in the MMU. The TLBis a cache of previously translated addresses. Thus, when a request isreceived for a memory access that includes an address to be translated,the TLB is checked first. If the address and its translation are in theTLB, then no further translation process based on using any number oftranslation techniques is necessary. Otherwise, the received address istranslated using one of any number of translation techniques.

A further embodiment of a computing environment to incorporate and useone or more aspects of the dynamic code optimization capability,including the partition mobility facility, is depicted in FIG. 2A.Referring to FIG. 2A, in one example, a computing environment 200includes a central processor complex (CPC) 202 coupled to one or moreinput/output (I/O) devices 204 via one or more control units 206.Central processor complex 202 includes processor memory 208 (a.k.a.,main memory, main storage, central storage) coupled to one or morecentral processors (a.k.a., central processing units (CPUs)) 210 and anI/O subsystem 212, each of which is further described below.

Processor memory 208 includes one or more virtual machines 214 (for oneexample of the PowerPC architecture) or one or more logical partitions214 (for one example of the z/Architecture), and processor firmware 216,which includes a hypervisor 218 and other processor firmware 220. Asused herein, firmware includes, e.g., the microcode and/or millicode ofthe processor. It includes, for instance, the hardware-levelinstructions and/or data structures used in implementation of higherlevel machine code. In one embodiment, it includes, for instance,proprietary code that is typically delivered as microcode that includestrusted software or microcode specific to the underlying hardware andcontrols operating system access to the system hardware.

Each virtual machine or logical partition 214 functions as a separatesystem and has one or more applications 222, and optionally, a residentoperating system 224 therein, which may differ for each virtual machineor logical partition. In one embodiment, the operating system is thez/VM operating system, the z/OS operating system, the z/Linux operatingsystem, the TPF operating system, the AIX operating system, the PowerLinux operating system, the IBM i/OS operating system, or anotheroperating system, offered by International Business MachinesCorporation, Armonk, N.Y., or another operating system offered byanother company. Further, each logical partition or virtual machine mayinclude a dynamic code optimizer 225 or other optimizer that may executeas part of the operating system, part of one or more applications or onits own to provide optimized application code.

The virtual machines are managed by hypervisor 218, such as PowerVM,offered by International Business Machines Corporation, Armonk, N.Y.;and the logical partitions are managed by hypervisor 218, such as theProcessor Resource/System Manager (PR/SM), offered by InternationalBusiness Machines Corporation, Armonk, N.Y.

Central processors 210 are physical processor resources assignable tothe virtual machines or allocated to the logical partitions. Forinstance, each virtual machine or logical partition 214 includes one ormore logical processors, each of which represents all or a share of aphysical processor 210 that may be dynamically allocated to the virtualmachine or partition. A central processor may include a memorymanagement unit (MMU) 230 and one or more address translation structures231 providing address translation, as described herein, and at least onecache 232.

Input/output subsystem 212 directs the flow of information betweeninput/output devices 204 and main memory 208. It is coupled to thecentral processing complex, in that it can be a part of the centralprocessing complex or separate therefrom. The I/O subsystem relieves thecentral processors of the task of communicating directly with theinput/output devices and permits data processing to proceed concurrentlywith input/output processing. To provide communications, the I/Osubsystem employs I/O communications adapters. There are various typesof communications adapters including, for instance, channels, I/Oadapters, PCI cards, Ethernet cards, Small Computer Storage Interface(SCSI) cards, etc. Further, the I/O subsystem uses one or moreinput/output paths as communication links in managing the flow ofinformation to or from input/output devices 204.

In accordance with one aspect, a partition running on a machine (orsystem or host) may be migrated to another machine, as described herein.In this context, the term partition may refer to a logical partition orto a virtual machine, as examples. For instance, with reference to FIG.2B, a first machine 250 includes a plurality of partitions 260 a-260 n,and a second machine 252 includes one or more other partitions 270. Inone example, Partition 1, and in particular, the applications ofPartition 1 are to be migrated from machine 1 to machine 2, as shown bythe dotted line. One embodiment of such migration is described below.

Another embodiment of a computing environment to incorporate and use oneor more aspects of the dynamic code optimization capability, includingthe partition mobility facility, is described with reference to FIG. 3A.In this example, a computing environment 300 includes, for instance, anative central processing unit (CPU) 302, a memory 304, and one or moreinput/output devices and/or interfaces 306 coupled to one another via,for example, one or more buses 308 and/or other connections. Asexamples, computing environment 300 may include a PowerPC processor, ora Power Systems server offered by International Business MachinesCorporation, Armonk, N.Y.; an HP Superdome with Intel Itanium IIprocessors offered by Hewlett Packard Co., Palo Alto, Calif.; and/orother machines based on architectures offered by International BusinessMachines Corporation, Hewlett Packard, Intel, Oracle, or others.

Native central processing unit 302 includes one or more native registers310, such as one or more general purpose registers and/or one or morespecial purpose registers used during processing within the environment,as well as one or more address translation structures 311. Theseregisters include information that represents the state of theenvironment at any particular point in time.

Moreover, native central processing unit 302 executes instructions andcode that are stored in memory 304. In one particular example, thecentral processing unit executes emulator code 312 stored in memory 304.This code enables the computing environment configured in onearchitecture to emulate another architecture. For instance, emulatorcode 312 allows machines based on architectures other than thez/Architecture, such as PowerPC processors, Power Systems servers, HPSuperdome servers or others, to emulate the z/Architecture and toexecute software and instructions developed based on the z/Architecture,or allows machines based on architectures other than the PowerArchitecture, such as HP Superdome servers or others, to emulate thePower Architecture and to execute software and instructions developedbased on the Power Architecture.

Further details relating to emulator code 312 are described withreference to FIG. 3B. Guest instructions 350 stored in memory 304comprise software instructions (e.g., correlating to machineinstructions) that were developed to be executed in an architectureother than that of native CPU 302. For example, guest instructions 350may have been designed to execute on a Power Architecture orz/Architecture processor 102, but instead, are being emulated on nativeCPU 302, which may be, for example, an Intel Itanium II processor. Inone example, emulator code 312 includes an instruction fetching routine352 to obtain one or more guest instructions 350 from memory 304, and tooptionally provide local buffering for the instructions obtained. Italso includes an instruction translation routine 354 to determine thetype of guest instruction that has been obtained and to translate theguest instruction into one or more corresponding native instructions356. This translation includes, for instance, identifying the functionto be performed by the guest instruction and choosing the nativeinstruction(s) to perform that function.

Further, emulator code 312 includes an emulation control routine 360 tocause the native instructions to be executed. Emulation control routine360 may cause native CPU 302 to execute a routine of native instructionsthat emulate one or more previously obtained guest instructions and, atthe conclusion of such execution, return control to the instructionfetch routine to emulate the obtaining of the next guest instruction ora group of guest instructions. Execution of the native instructions 356may include loading data into a register from memory 304; storing databack to memory from a register; or performing some type of arithmetic orlogic operation, as determined by the translation routine.

Each routine is, for instance, implemented in software, which is storedin memory and executed by native central processing unit 302. In otherexamples, one or more of the routines or operations are implemented infirmware, hardware, software or some combination thereof. The registersof the emulated processor may be emulated using registers 310 of thenative CPU or by using locations in memory 304. In embodiments, guestinstructions 350, native instructions 356 and emulator code 312 mayreside in the same memory or may be disbursed among different memorydevices.

The computing environments described above are only examples ofcomputing environments that can be used. Other environments, includingbut not limited to, other non-partitioned environments, otherpartitioned environments, and/or other emulated environments, may beused; embodiments are not limited to any one environment.

Computing environments, such as those described above, are enhanced byincluding components that alter application programs executing withinthe environments to provide those application programs with additionalfeatures. For instance, a component, referred to as dynamic codeoptimization (DCO), may be provided that examines programs as they areexecuting, recognizes frequently executed code segments and optimizesthose segments. Other types of optimization are also possible, as wellas other types of components. Further, changes may be made to programsfor other reasons, such as correcting an error, providing workaroundsfor known hardware errata, enhancing security, etc.

Changing a program while it is executing is complicated and issues mayarise. For instance, if a program references itself, i.e., it isself-referential, it may detect the change and refuse to run or thechange may cause it to run improperly due to it being self-referential.An example of a self-referential code may be a binary that validates itsown correctness by computing the checksum of its program code, andcomparing the computed result with an expected result to avoidtampering. Thus, in accordance with one aspect, a capability is providedthat allows applications to be modified, while preservingself-referential integrity.

In one example, for dynamic code optimization, code that is notfrequently used is maintained unchanged, and code that is frequentlyused, referred to as hot spots, are dynamically compiled into optimizedcode and the pre-existing code is patched to integrate the optimizedcode into the pre-existing code generating patched code. Then, totransfer to the optimized code, the original binary is modified(patched) by inserting a jump instruction to jump to the optimized codeand when done, another jump instruction is inserted to jump back to theoriginal code.

One example of a computing environment that includes patched code isdepicted in FIG. 4. This computing environment is based, for instance,on the PowerPC architecture offered by International Business MachinesCorporation, however many other systems may incorporate and use one ormore of the aspects described herein. As shown, a computing environment400 includes, for instance, a processor 402 coupled to a memory 404 viaone or more caches 406, 408. Memory 404 is, for instance, random accessmemory, having a plurality of portions, including, for example, systemmemory 410, data memory 412, and code memory 414 (also referred to asinstruction memory). In one example, system memory 410 includesapplication code, including, for instance, patched application code 420,and/or data for one or more applications; data memory 412 is memory usedby, for instance, an optimizer; and code memory 414 is, for instance,code of the optimizer. Code memory 414 is coupled to instruction cache406 accessed by processor 402; and data memory 412 and system memory 410are coupled to data cache 408 accessed by processor 402. Further, systemmemory 410, including patched application code 420, is also coupled toinstruction cache 406.

In particular, in one embodiment, system memory 410 includes, forinstance, application code for one or more applications, includingpatched application code 420. For example, application code for aparticular application is stored in one or more memory regions (e.g.,pages) of system memory 410. If the particular application is modified,then it is referred to as patched application code, which includes theexisting code plus the modified code. From a memory viewpoint, theportions of the patched application code that have not been modifiedcontinue to be stored in the same memory regions as the pre-existingapplication code, and any duplicated or modified code is stored in oneor more memory regions of system memory 410 separate from the memoryregions of the pre-existing or unmodified application code.

Since the patched application code includes modified code located in oneor more separate memory regions and since, in one embodiment, thismodified code is to be hidden from data accesses, separate addresstranslations for instruction fetches and data accesses relating to themodified code are provided, as described below. The use of separateaddress translations for instruction/data accesses, in conjunction withthe memory mapping of FIG. 4, allows the view of memory from theinstruction fetcher to be fenced off, enabling the use of patched codewhile maintaining referential integrity.

Details regarding physical memory used by one or more of the computingenvironments described herein and access thereto are described withreference to FIG. 5. As is known, physical memory is of a defined sizeand in order to have the physical memory appear larger than it is,virtual memory is utilized. One example of a high-level view of virtualmemory 501 mapped to a physical memory 503 (such as memory 108, 208,304, 404 or a portion thereof) is depicted in FIG. 5. In this example,the mapping from virtual memory to real memory is via a hash page table(HPT) technique 505 to locate page table entries (PTEs), as used by, forexample, Power ISA. In this example, programs only use sections (orsegments) A and B of the virtual memory. Each segment of the virtualmemory is mapped to a segment identifier (SID) entry 507 identified byan effective segment ID (ESID) (ESIDs for B and ESIDs for A included).An “effective address” 504 used by the program selects an SID entry,which includes the ESID value, as well as a virtual segment ID (VSID)514 value. The VSID value represents the high-order bits of a virtualaddress to be used by hashing algorithm 505 to search the hash pagetable. A hashed value based on the VSID is used to locate a page tableentry (PTE). The page table entry includes an address 513 of a page ofphysical memory 503.

As indicated above, an effective address is used to obtain a physicaladdress in order to access a particular memory location. In accordancewith one aspect, as depicted in FIG. 6, one effective address 600 in aneffective address space 602 may translate to multiple physical addresses604 a, 604 b of a physical address space 606 depending on whether thetranslation is for an instruction translation 608 or a data translation610. In particular, in one embodiment, separate address translation(i.e., separate instruction and data translation) may be used in certainsituations, such as for instance, when code has been modified, but themodified code is to be hidden from data accesses. In such a situation,the modified code is placed in a separate memory region at a differentphysical address than the unmodified code, and the physical address ofthe separate memory region is determined via address translation forinstruction fetches. The unmodified code, however, is still accessed bydata accesses, which use address translations for data accesses thatpoint to another physical address (i.e., of the unmodified code). Thisallows, for instance, the view of memory the instruction fetcher sees tobe fenced off from the view of the data accesses. For those situations,where the code is unchanged, address translation for instruction fetchesand data accesses point to the same physical memory locations. Theselocations are referred to as being shared for instruction fetches anddata accesses.

In accordance with one aspect, an address translation capability isdescribed in which the address translation takes into considerationwhether the memory access is for an instruction fetch or a data access.One embodiment of address translation is described with reference toFIGS. 7-10. The particular example described herein is for the PowerPCarchitecture; however, aspects of the address translation capability arenot limited to such an architecture.

Initially, referring to FIG. 7, a memory management unit (MMU) of aprocessor receives an effective address to be translated, STEP 700. Theeffective address is, for instance, a 64-bit address that may bereceived in an address translation request from the processor. Asexamples, the request may be from an instruction fetch unit of theprocessor, and therefore, the address to be translated is assumed to befor an instruction fetch, or the request may be from a load/store unitof the processor, and therefore, the address to be translated is assumedto be for a data access. In other embodiments, an indication in therequest indicates whether the address translation is for an instructionfetch or a data access. The MMU translates the effective address to avirtual address, STEP 702. In one example, the translation from theeffective address to the virtual address uses a segment lookaside buffer(SLB), as described further below. The MMU then translates the virtualaddress to a physical address, STEP 704. In one particular example, thetranslation from the virtual address to the physical address uses a hashpage table, again as described further below. The MMU then uses thephysical address to access the particular memory location, STEP 706.

Further details regarding translating from the effective address to thevirtual address, by, for instance, the MMU are described with referenceto FIGS. 8 and 9. Referring initially to FIG. 8, the MMU receives aneffective address via, for instance, an address translation request sentfrom a particular unit (e.g., instruction fetch, load/store unit) of theCPU, STEP 800. Based on receiving the effective address, the MMUdetermines whether the address is for an instruction fetch or a dataaccess. This can be determined, in one example, based on which unit(e.g., fetch unit or load/store unit of the CPU) the MMU received theaddress translation request or by an indicator associated with therequest, as examples. For instance, if the address translation requestcame from the fetch unit, then it is assumed that the request is for aninstruction fetch, and if it came from the load/store unit, it isassumed it is for a data access. Based on receiving the effectiveaddress, the MMU obtains an effective segment identifier from theeffective address, STEP 802. The MMU then uses the effective segmentidentifier to search a segment lookaside buffer for a matching entry,STEP 804.

In particular, as shown in FIG. 9, in one embodiment, an effectiveaddress 900 is a 64-bit address including an effective segmentidentifier (ESID) 902, a page offset 904, and a byte offset 906. Theeffective segment identifier is extracted 910 from the effective addressand used to search a segment lookaside buffer (SLB) 912 for a matchingentry 914. A segment lookaside buffer (SLB) 912 is a cache of recentlyaccessed segment ID entries. In one example, it is located in the MMU,but in other examples, it is located elsewhere. It specifies the mappingbetween effective segment IDs (ESIDs) and virtual segment IDs (VSIDs).The number of SLB entries (SLBE) in an SLB is implementation dependent,and in one example, includes at least 32 entries. In one example,segment lookaside buffer 912 includes a plurality of SLB entries 914,and each SLB entry 914 maps one ESID 902 to one VSID 916. In oneexample, SLBE 914 includes the following fields:

-   -   Effective segment ID (ESID) 902 (bits 0-35);    -   Entry valid indicator (V) 922 (bit 36) which indicates whether        the entry is valid (V=1) or invalid (V=0);    -   Segment size selector (B) 924 (bits 37-38), which has the        following meaning, in one example: 0b00—256 Megabytes (MB)        (s=28); 0b01—1 Terabyte (TB) (s=40); 0b10—256 TB (s=48); and        0b11—reserved;    -   Virtual segment ID (VSID) 916 (bits 39-88);    -   Supervisor (privileged) state storage key indicator (K_(s)) 928        (bit 89);    -   Problem state storage key indicator (K_(p)) 930 (bit 90);    -   No-execute segment if N=1 indicator (N) 932 (bit 91).        Instructions cannot be executed from a No-execute (N=1) segment;    -   Virtual page size selector bit 0 (L) 934 (bit 92);    -   Class indicator (C) 936 (bit 93);    -   The Class field of the SLBE is used in conjunction with, for        instance, slbie (SLB invalidate entry) and slbia (SLB invalidate        all) instructions. “Class” refers to a grouping of SLB entries        and implementation-specific lookaside information so that only        entries in a certain group need be invalidated and others might        be preserved. The Class value assigned to an        implementation-specific lookaside entry derived from the SLB        entry is to match the Class value of that SLB entry. The Class        value assigned to an implementation-specific lookaside entry        that is not derived from an SLB entry (such as real mode address        “translations”) is 0.    -   Virtual page size selector bits 1:2 (LP) 938 (bits 95-96);    -   Segments may contain a mixture of page sizes. The L and LP bits        specify the base virtual page size that the segment may contain.        The SLB_(L∥LP)) encoding are those shown below, in one example.        The base virtual page size (also referred to as the “base page        size”) is the smallest virtual page size for the segment. The        base virtual page size is 2^(b) bytes. The actual virtual page        size (also referred to as the “actual page size” or “virtual        page size”) is specified by PTE_(L∥LP), where ∥ is a        concatenation of the two values.

Encoding Page Size 0b000  4 KB 0b101 64 KB additional values¹ 2^(b)bytes, where b > 12 and b may differ among encoding values ¹In oneembodiment, the “additional values” are implementation-dependent, as arethe corresponding base virtual page sizes. Any values that are notsupported by a given implementation are reserved in that implementation,in at least one embodiment.

-   -   No Access (NOA) indicator 940 (bits 97:98), which NOA₀=No        Instruction (NOI); NOA₁=No Data (NOD); 0b00—SLBE can be used for        both instruction fetches and data accesses; 0b01—SLBE can only        be used for instruction fetches; 0b10—SLBE can only be used for        data accesses; and 0b11—reserved.

For each SLB entry, software is to ensure the following requirements aresatisfied.

-   -   L∥LP contains a value supported by the implementation.    -   The base virtual page size selected by the L and LP fields does        not exceed the segment size selected by the B field.    -   If s=40, the following bits of the SLB entry contain 0s.        -   ESID_(24:35)        -   VSID_(39:49)    -   The bits in the above two items are ignored by the processor.

In accordance with one aspect, the NOA field specifies for each SLBentry whether the SLB entry is to be used to translate an effectivememory address to a virtual address for instruction fetch and dataaccess (NOA=0b00, in one encoding of allowed accesses for a segment inaccordance with one aspect), for data accesses but not instruction fetch(NOA=0b10, in one encoding of allowed accesses for a segment inaccordance with one aspect), and for instruction fetch but not dataaccess (NOA=0b01, in one encoding of allowed accesses for a segment inaccordance with one aspect).

It is legal to have multiple effective to virtual segment idtranslations, as long as only one is selected to be performed based onthe NOA bits. To accomplish this, software is to ensure that the SLBcontains at most one entry that translates a given instruction effectiveaddress, and that if the SLB contains an entry that translates a giveninstruction effective address (NOA₀=0), then no other entry cantranslate the same address for instruction fetches. In accordance withone aspect, when installing a new SLB entry for one or more access modes(e.g., instruction fetch), software is to ensure that any previouslyexisting SLB translation entry of that effective address that maytranslate an address for such access mode has been invalidated.Likewise, software is to ensure that the SLB contains at most one entrythat translates a given data effective address (NOA₁=0), and that if theSLB contains an entry that translates a given data effective address,then any previously existing translation of that effective address fordata accesses has been invalidated. An attempt to create an SLB entrythat violates these requirements may cause a machine check. Inaccordance with one embodiment, a machine check is a high priorityinterrupt to a firmware, hypervisor or other supervisor component toindicate that system integrity constraints have been violated.

In accordance with one embodiment, it is permissible for software toreplace the contents of a valid SLB entry without invalidating thetranslation specified by that entry provided the specified restrictionsare followed.

When the hardware searches the SLB, all entries are tested for a matchwith the effective address (EA). For a match to exist, the followingconditions are to be satisfied for indicated fields in the SLBE.

-   -   V=1 (i.e., the valid bit is set for an entry)    -   ESID_(0:63-s)=EA_(0:63-s), where the value of s is specified by        the B field in the SLBE being tested.    -   The search is an instruction address search and NOI=0, or the        search is a data address search and NOD=0.

In particular, in one embodiment, an entry in the SLB is matching if theentry is valid, has an effective segment identifier matching theobtained effective segment identifier from the effective address, andthe No Access (NOA) SLB field is set for the type of memory access beingperformed, e.g., for an instruction fetch or a data access. The NOAincludes, for instance, two bits, in which a value of 01 indicates anaddress can be used to match addresses associated with instructionaccess only; 10 indicates an entry can be used to match addressesassociated with data access only; and 00 indicates an entry can be usedto match addresses associated with both instruction fetches and dataaccesses. If the NOA field is set for the requested access and theeffective SID is the same as the obtained effective SID, then there is amatch.

Returning to FIG. 8, a determination is made as to whether a matchingentry in the SLB was found, INQUIRY 806. In particular, the matchinglogic is performed in conjunction with the NOA field of FIG. 9indicating the types of accesses each particular SLBE may translate. Ifno matching entry was found, then there is indicated an SLB missexception, which transfers control to a software handler for handlingthe exception, STEP 808. In at least one embodiment, the softwarehandler manages the SLB as a cache and reloads a new SLB entry (SLBE)from a table of SLBEs maintained in memory. If, however, a matchingentry is found, INQUIRY 806, then a determination is made as to whethermultiple matching entries were found, INQUIRY 810. If there are multiplematches, a machine check may be taken, STEP 812, since there should notbe multiple matches, or in another embodiment, one of the entries isselected and used.

However, if there is one match (or one is selected), a virtual segmentidentifier (VSID) 916 (FIG. 9) in the SLB entry is extracted 920 andused as part of the virtual address. The VSID is concatenated with pageoffset 904 and byte offset 906 from the effective address to create thevirtual address. This virtual address is then returned, STEP 814 (FIG.8).

As described above, for the SLB search, if no match is found, the searchfails. If one match is found, the search succeeds. If more than onematch is found, one of the matching entries may be used as if it werethe only matching entry, or a machine check occurs. If the SLB searchsucceeds, the virtual address (VA) is formed from the EA and thematching SLB entry fields as follows: VA=VSID_(0:77-s)∥EA_(64-s:63). TheVirtual Page Number (VPN) is bits 0:77-p of the virtual address. Thevalue of p is the actual virtual page size specified by the PTE used totranslate the virtual address. If SLBE_(N)=1, the N (noexecute) valueused for the storage access is 1.

On an instruction fetch, if SLBE_(N)=1, an Instruction Storage interruptmay occur without the page table being searched. If the SLB searchfails, a segment fault occurs. This is an instruction segment exceptionor a data segment exception, depending on whether the effective addressis for an instruction fetch or for a data access.

The virtual address created from translation of the effective address isthen translated to a physical address (a.k.a., a real address) using,for instance, a hash page table. Further details regarding translationusing a hash page table are described with reference to FIG. 10.

In particular, FIG. 10 illustrates one example of a hash page table(HPT) translation structure used by Power ISA. ESID portion 1006 of aneffective address (EA) 1004 is used to locate an entry in SLB 1012. Theentry includes a VSID field 1014. The value of VSID field 1014 and thepage portion 1008 of EA 1004 are hashed 1030 to produce a hash valuethat is used to locate a page table entry (PTE) group 1052 in a hashpage table (HPT) 1050. (In another embodiment, since the virtual addresswas previously created, the VSID and page portion may be extracteddirectly from the formed virtual address.) In at least one embodiment,the hash page table is located by a page table origin address providedby the processor. Page table entries 1053 of PTE group 1052 are searchedto locate a corresponding PTE having a field matching a value of amost-significant-portion of the VSID. When a corresponding PTE is found,the address (e.g., real address) of the physical memory page in the PTEis used to access physical memory. In order to improve performance, oncea PTE entry is found, the page portion 1008 of EA 1004 and the addressof the physical memory page found in the PTE are stored in TLB 1054,such that further accesses to the same EA page will “hit” in TLB 1054and avoid the PTE search.

As described above, in one example, address translation is performedbased on a particular attribute, such as, for instance, the type ofaccess: instruction fetch or data access. To enable this, a mechanism isprovided that includes a field in the SLB to prevent SLBEs from beingused for instruction-side or data-side accesses. This field, asindicated above, is the No Access (NOA) field. The NOA is used toindicate that a particular SLBE associated with the NOA can be used foronly instruction fetches, only data accesses, or for both instructionfetches and data accesses (e.g., when the code is not modified).

In accordance with one embodiment, the NOA field is separately specifiedfor each segment in conjunction with an SLB entry, thereby allowing someeffective address segments (memory regions of the input address) to betranslated to a common segment address for instruction and data accesses(memory regions of the output address), and other segments (memoryregions of the input address) to be translated to separate segmentaddresses for instruction and data accesses (memory regions of theoutput address), respectively, or to provide a translation for one typeof access (e.g., instruction access), but not another type of access(e.g., data access) by loading an appropriate SLB entry for one type ofaccess, but not another. While the description has been made withrespect to the presence of a NO Access field, and to a specific encodingof a NO Access field in the SLB, it is understood that other fields,other encodings for such fields, or both, may be used to identify thetypes of permissible access for a translation.

As described herein, in accordance with one or more aspects, theseparate instruction/data address translation technique is used toredirect address translation to a particular region of memory thatincludes modified code for instruction fetches and another region ofmemory that includes the unmodified code for data accesses, as shown inFIG. 11. In one or more examples, an SLB-based mechanism, as describedabove, may be used or other types of mechanisms, which are based, forinstance on hierarchical or radix address translation structures. Insuch a hierarchical based mechanism, in one embodiment, an attributeindicator is provided in an entry of one of the structures in thehierarchy which directs which path is taken to translate an address.This path may select, e.g., instruction access only, data access only,or a shared access

Referring to FIG. 11, in one example, patched application code 420includes a modified portion, and that modified portion is stored in oneor more memory regions 1100 of system memory 410. The unmodified portioncontinues to be in other memory regions 1102 of system memory 410. Inparticular, the other memory regions 1102 include the application priorto modification.

In this embodiment, an effective address 600 is used to access memoryregion 1100 or memory region 1102 depending on whether the addresstranslation is for an instruction fetch 608 for a modified portion or adata access 610 for an unmodified portion. If, for instance, thetranslation is for an instruction fetch of a modified portion, theneffective address 600 is translated to physical address 604 a, whichpoints to memory region 1100 that includes modified code. However, ifthe address translation is for a data access, then effective address 600is translated to physical address 604 b, which points to memory region1102, which includes the unmodified, pre-existing or original codecorresponding to the modified code.

In a further embodiment, with reference to FIG. 12, an effective address1200 may use a shared translation 1202, in which a same memory region1204 is used for an instruction fetch and a data access (since, forinstance, that code portion has not been modified). In this example,effective address 1200 is translated to a physical address 1206, whichpoints to memory region 1204.

The address translation capability described above is used, in one ormore examples, in environments that provide dynamic code optimization.Dynamic code optimization (a.k.a., dynamic compilation and optimization)offers significant opportunities to improve the operation of computersystems. For instance, existing code can be modified to improveperformance by re-optimizing hot regions, avoiding errors, correctingfor errors, enhancing or changing security, providing additionalfeatures, etc. In accordance with one aspect, dynamic code optimizationis used to exploit extended mode features for a selected application,while preventing other applications from exploiting the features. Thatis, the optimizer (e.g., dynamic code optimizer) sets one or morecontrols at an application level to enable the application to exploitextended mode features. As used herein, the setting of the one or morecontrols by the optimizer includes, for instance, the optimizer settingthe controls, assuming the optimizer has such authority, and/or theoptimizer directing a component that has authority, such as theoperating system or hypervisor, to perform the actual setting,particularly when the optimizer lacks such authority.

As used herein, an optimizer refers to, for instance, a dynamic codeoptimizer, a compiler that performs optimization, such as a Just-In-Time(JIT) compiler, binary translators, as well as other components thatprovide optimization, as examples.

The extended mode features include, for instance, extended ISA features,in which DCO generated code executing with normal application levelprivilege is provided access to extended features, either those that areabove a partition's or application's selected ISA level, or privateimplementation specific non-architected capabilities, including highperformance modes, high performance instructions and/or high performanceresources otherwise known or unavailable to the application, as justsome examples.

An example of an above-level ISA is using instructions that are notavailable at the ISA level the application is executing (e.g., usingvector-scalar (VSX) instructions when the ISA level is set to Power6,which did not offer VSX instructions).

An example of a high performance mode is an alternate mode where adifferent ISA is executed. Examples of such ISAs may be a VLIW ISA (VeryLong Instruction Words offer enhanced software control of parallelism byallowing a compiler to specify a plurality of instructions to beperformed in parallel) or a Wide-Word Power ISA (WW-Power) where eachPower instruction has more than 32b, to give access to additionalfunctions, wider displacements, and so forth.

Examples of non-architected high performance instructions are additionalmove instructions to move data directly between register files ofdifferent types, a branch to TAR (target address register) instruction,or additional prefetch control instructions, as examples.

An example of high performance resources are extensions to provideadditional registers, either as part of the general purpose registers,floating point registers or vector scalar register sets, or additionalspecial purpose registers, such as a TAR register.

The above-described types of enhancements are collectively referred toherein as extended mode features, which are features known to theoptimizer, but unknown or unavailable to the application, unless enabledby the optimizer. Again, as a few examples, these extended mode featuresinclude, for instance, extended ISA features (e.g., features at a higherlevel than the level at which the application is executing); alternateISA modes; non-architected high performance instructions; highperformance resources; etc. Other features may also be consideredextended mode features, as described herein.

In accordance with one or more aspects, the optimizer sets one or morecontrols, referred to, e.g., as extended mode controls, to selectivelyprovide extended mode features for an application. As described herein,the extended mode controls may include one or more of: one or moreextended mode enable facilities, and/or one or more extended modecontrol authorization facilities, each of which is described below.

Examples of controls that may be used to provide extended mode featuresare described with reference to FIGS. 13A-13F. For instance, withreference to FIG. 13A, one or more controls are provided in a controlregister 1300. Control register 1300 includes selected information,including, for instance, one or more extended mode controls 1302, thatare used to indicate whether extended mode features are available for anapplication. Examples of such a control register include a machine stateregister (MSR) or a program status word (PSW).

Referring to FIG. 13B, in one example, a machine state register 1310includes selected information, including one or more extended modecontrols 1312. In one particular embodiment, the machine state register(MSR) is a 64-bit register that defines the state of a thread, and theselected information includes, for instance, the following definitions:

Bit Description  0 Sixty-Four Bit Mode (SF) 0 The thread is in 32-bitmode 1 The thread is in 64-bit mode  1:2 Reserved  3 Hypervisor State(HV) 0 The thread is not in hypervisor state 1 If MSR_(PR) = 0 thethread is in hypervisor state; otherwise the thread is not in hypervisorstate.  4 Extended Mode Enable Facility 0 Extended mode is disabled -Code, e.g., code generated by the optimizer, cannot use extended modefacility. 1 Extended mode is enabled - Code, e.g., code generated by theoptimizer, is authorized to use extended mode facility.  5 Split LittleEndian (SLE) 0 Instruction and data storage accesses for the thread arethe same and use the value specified by MSR_(LE). 1 Instruction and datastorage accesses for the thread are opposite. Instruction storageaccesses use the value specified by MSR_(LE). Data storage accesses usethe value specified by

 MSR_(LE).  6 Extended Mode Control Authorization Facility 0 Application(user mode) is not allowed to use extended mode control features, andextended mode enable facility cannot be set by user mode code. 1Application (user mode) is allowed to use extended mode controlfeatures, and extended mode enable facility can be set by user modecode.  7:28 Reserved 29:30 Transaction State (TS) [Category:Transactional Memory] 00  Non-transactional 01  Suspended 10 Transactional 11  Reserved 31 Transactional Memory Available (TM)[Category: Transactional Memory] 0 The thread cannot execute anytransactional memory instructions or access any transactional memoryregisters. 1 The thread can execute transactional memory instructionsand access transactional memory registers unless the transactionalmemory facility has been made unavailable by some other register. 32:37Reserved 38 Vector Available (VEC) [Category: Vector] 0 The threadcannot execute any vector instructions, including vector loads, stores,and moves. 1 The thread can execute vector instructions unless they havebeen made unavailable by some other register. 39 Reserved 40 VSXAvailable (VSX) 0 The thread cannot execute any VSX instructions,including VSX loads, stores, and moves. 1 The thread can execute VSXinstructions unless they have been made unavailable by some otherregister. 41:47 Reserved 48 External Interrupt Enable (EE) 0 External,decrementer, performance monitor <S>, and privileged doorbell interrupts<S.PC.> are disabled. 1 External, decrementer, performance monitor <S>,and privileged doorbell interrupts <S.PC.> are enabled. 49 Problem State(PR) 0 The thread is in privileged state. 1 The thread is in problemstate. 50 Floating Point Available (FP) [Category: Floating Point] 0 Thethread cannot execute any floating point instructions, includingfloating point loads, stores and moves. 1 The thread can executefloating point instructions unless they have been made unavailable bysome other register. 51 Machine Check Interrupt Enable (ME) 0 Machinecheck interrupts are disabled. 1 Machine check interrupts are enabled.52 Floating Point Exception Mode 0 (FE0) [Category: Floating Point] Seebelow. 53 Single Step Trace Enable (SE) [Category: Trace] 0 The threadexecutes instructions normally. 1 The thread generates a single steptype trace interrupt after successfully completing the execution of thenext instruction, unless that instruction is a defined instruction whichis not traced. Successful completion means that the instruction causedno other interrupt and, if the processor is in the transactional state<TM>, is not one of the instructions that is forbidden in transactionalstate. 54 Branch Trace Enable (BE) [Category: Trace] 0 The threadexecutes branch instructions normally. 1 The thread generates a branchtype trace interrupt after completing the execution of a branchinstruction, whether or not the branch is taken. Branch tracing need notbe supported on all implementations that support the trace category. Ifthe function is not implemented, this bit is treated as reserved. 55Floating Point Exception Mode 1 (FE1) [Category: Floating Point] Thefloating point exception mode bits FE0 and FE1 are interpreted as shownbelow. FE0 FE1 Mode 0 0 Ignore Exceptions 0 1 Imprecise Non-recoverable1 0 Imprecise Recoverable 1 1 Precise 56:57 Reserved 58 InstructionRelocate (IR) 0 Instrution address translation is disabled. 1Instruction address translation is enabled. 59 Data Relocate (DR) 0 Dataaddress translation is disabled. Effective Address Overflow (EAO) doesnot occur. 1 Data address translation is enabled. EAO causes a datastorage interrupt. 60 Reserved 61 Performance Monitor Mark (PMM)[Category: Server] For use in indicating whether certain performancecounters are to count events for selected processes. 62 RecoverableInterrupt (RI) 0 Interrupt is not recoverable. 1 Interrupt isrecoverable. 63 Little-Endian Mode (LE) 0 Instruction and data storageaccesses for the thread are in Big Endian mode when MSR_(SLE) = 0. WhenMSR_(SLE) = 1, instruction storage accesses are in Big Endian mode anddata storage accesses are in Little Endian mode. 1 Instruction and datastorage accesses for the thread are in Little Endian mode when MSR_(SLE)= 0. When MSR_(SLE) = 1, instruction storage accesses are in LittleEndian mode and data storage accesses are in Big Endian mode.

In accordance with one embodiment, extended mode features (also referredto as high speed mode) are enabled by an extended mode enable facility,as shown in one example as being assigned to a bit position 4 of amachine state register. When this bit is set to 1, it enables extendedmode features, such as, for example, including one or more of thefollowing:

(1) Instructions available on a specific hardware implementation butdisabled by way of the setting of a virtual architecture level lowerthan the architecture level implemented by the present implementation,e.g., using a processor compatibility register (PCR) in accordance withthe Power ISA (Instruction Set Architecture), or a Virtual ArchitectureLevel (VAL) setting in accordance with the System z ISA;

(2) Instructions corresponding to implementation specific extensions notspecified by any corresponding ISA level, e.g., instructions generallyreserved for use by the microcode;

(3) Instructions that are limited to execution by microcode, millicode,firmware, or privileged software;

(4) Instructions that are otherwise part of separately controlledsubsets, e.g., including, but not limited to, those of the FPU (floatingpoint), VMX (vector media extensions), and VSX (vector scalar)facilities in accordance with the Power ISA, or extended facilities ofthe Power ISA;

(5) An ISA separate and/or distinct from the published ISA, such as aVLIW or WW_Power ISA, and so forth.

In at least one other embodiment, a plurality of extended mode enablefacilities (e.g., a plurality of bits) are provided, and each of theplurality of extended mode enable facilities offers individual access toone or more extended features including, but not limited, to the onesdescribed herein.

In accordance with one embodiment, a separate extended mode controlauthorization facility is provided, as shown in accordance with oneembodiment as being assigned to a bit position 6 of a machine stateregister. In accordance with one embodiment, an extended mode controlauthorization facility is provided to control an application's abilityto modify the extended mode enable facility and thereby gain access toextended mode features. In accordance with at least one aspect, onlysome applications are enabled with access to the extended mode enablefacility. In one embodiment, these applications correspond to one ormore of those being used in conjunction with dynamic code optimization,binary translation, and Just-in-Time compilation, in accordance with oneor more aspects.

In at least one embodiment, the extended mode control authorizationfacility also gives applications the ability to control access to enableone or more restricted and separately controlled modes, e.g., thosecontrolled by MSR[FP], MSR[VEC] and MSR[VSX]. In at least oneembodiment, when the extended mode control authorization facility isenabled, user-level applications are also authorized to enable one ormore of these modes.

In addition to, or instead of, including one or more extended modecontrols (e.g., one or more extended mode enable facilities, and/or oneor more extended mode control authorization facilities) in a controlregister, such as a machine state register, a program status word, orother type of control register, extended mode controls can be includedin various address translation structures, as shown in FIG. 13C. Forinstance, a particular address translation structure includes aplurality of entries 1320, and each entry 1320 includes variousinformation to be used in translating an address. Further, in accordancewith one aspect, the information may also include one or more extendedmode controls 1322 to indicate whether application code corresponding tothe memory region being translated can use extended mode features. Forinstance, extended mode controls 1322 may indicate, e.g., whetherapplication code corresponding to the memory region being translated hasauthority to use extended mode features (e.g., extended mode controlauthorization facility), and/or whether the extended mode is enabled forapplication code corresponding to the memory region being translated(e.g., extended mode enable facility).

In one embodiment, one or more of the controls correspond to applicationcode with user privilege level, but not to code with supervisorprivilege level. In one embodiment, one or more of the controlscorrespond to partition-level code (i.e., code with user and operatingsystem privilege level), but not to code with hypervisor privilegelevel. In yet another embodiment, one or more of the controls correspondto code with user, operating system and hypervisor privilege level, butnot to code of yet another fourth privilege level, and so forth.

One particular address translation structure is a page table, and withreference to FIG. 13D, a page table entry 1330 is described, whichincludes selected information including one or more extended modecontrols 1332. In one particular example, the selected informationincludes address information (e.g., a page frame real address) used tocreate a physical address, as well as controls to control execution ofthe page associated with the physical address. These controls depend,for instance, on the system architecture; however, in accordance withone aspect, one or more of the controls include one or more of extendedmode controls 1332. As described above, one or more extended modecontrols 1332 are used to indicate whether application codecorresponding to the memory region being translated can use extendedmode features. For instance, extended mode controls 1322 may indicate,e.g., whether application code corresponding to the memory region beingtranslated has authority to use extended mode features (e.g., extendedmode control authorization facility), and/or whether the extended modeis enabled for application code corresponding to the memory region beingtranslated (e.g., extended mode enable facility).

In further examples, one or more extended mode controls may be includedin other address translation structures, such as a segment table entry(STE), region table entries (RTE), and/or other address translationentries that are used in translation, as well as to control memoryaccess.

Additionally, in a further example, one or more extended mode controlsmay be included in a storage key, an example of which is depicted inFIG. 13E. A storage key 1340 is associated with each 4K byte of realstorage, and is used to control access. In one example, it includesselected information, such as, e.g., access control bits, a fetchprotection bit, a reference bit and a change bit, as well as an extendedmode control 1342. Again, if the extended mode enable control is set to0, use of external mode control features is disabled, and if set to 1,use of external mode control features is enabled. Further, extended modecontrols 1342 may also include an extended mode control authorizationfacility.

In a further embodiment, instead of enabling/disabling extended modefeatures in totality, there may be separate controls for individualfeatures of the extended mode features. In this case, each controlregister, address translation entry or storage key would have multipleextended mode controls, one for each feature. For instance, there may bea plurality of extended mode enable facilities, one for each featuresuch that use of a particular feature may be enabled/disabled; and/orthere may be a plurality of extended mode control authorizationfacilities, one for each feature.

However, in one embodiment, to optimize the number of bits used in anaddress translation structure entry (e.g., a PTE, STE, RTE, SLBe etc.)or a storage key, as examples, but still enable multiple independentcontrols, a single bit is used to indicate whether a specific memoryregion (e.g., page, segment, region, etc.) is enabled to use theextended mode features, and then, a secondary set of bits is stored in,for instance, a control register (e.g., MSR, PSW) or a special purposeregister to determine which of a plurality of features is enabled by theDCO component. Similarly, a single bit may be stored in an addresstranslation structure or storage key for the extended mode controlauthorization facility, and then a secondary set of bits may be storedin a control register to determine which of a plurality of features isauthorized.

For instance, as shown in FIG. 13F, a page table entry 1350 includes anindicator (e.g., bit) 1352 that, if set to one, indicates, for instance,extended mode features are enabled for the application, but theparticular features 1354 that are enabled to be used are indicated, forinstance, in a control register, such as machine state register 1360.Indicator 1352 may similarly be used for the extended mode controlauthorization facility. In a further embodiment, control 1352 mayinclude two bits: one for the extended mode enable facility, and anotherfor the extended mode control facility, and then, the control registerincludes a secondary set of bits for each of those.

The control register indicating the selected extended mode features ismaintained, for instance, at the thread level, and context switches bythe operating system, give the DCO component separate control over thefeatures enabled for each application process. In other implementations,the extended mode controls are shared by all threads within a process,or by all processes within a partition, or by all threads within a core,and so forth, offering different levels of granularity.

In yet another embodiment, the extended mode control is implicitlyprovided in an entry of a segment lookaside buffer (SLBe). For instance,the extended mode control is shared with the No-data (NOA=D) bit of theSLBe. That is, in one example, when a page is not available for dataaccesses in a mapping—corresponding, e.g., to hidden code to ensure,e.g., correct self referential execution—additional functions that areonly to be made available to code generated by DCO are provided to codeexecuting from such pages. In one aspect, the extended mode control(e.g., single bit) enables a plurality of selections stored in an MSR,PSW, CR or SPR, as per above. In another aspect, the No-data access bitindicates whether or not extended modes are available with no furtherselection.

Embodiments of logic to perform optimization, and optionally, use theextended mode features, are described with reference to FIGS. 14A-15. Inparticular, FIG. 14A depicts one embodiment of generating optimized codewithout use of the extended mode control(s), and FIG. 14B depicts oneembodiment of generating optimized code using the extended modecontrol(s). Further, FIG. 15 depicts one embodiment of executing theoptimized code having the extended mode control(s).

Referring initially to FIG. 14A, a dynamic optimizer, such as a dynamiccode optimizer, is initiated within a processor (e.g., by the operatingsystem, an application, on its own, etc.), STEP 1400. The optimizeridentifies code to be patched, STEP 1402. For instance, the dynamic codeoptimizer identifies hot regions or areas in which the code may beoptimized. Based on identifying the code to be modified, new code isgenerated, STEP 1404. In one embodiment, this includes copying theportion of the code to be modified, and then, modifying that copiedportion, STEP 1404. The portion is copied, instead of copying the entireapplication. That is, only that portion to be modified is copied andstored in separate memory regions. The modifying may include any numberof known optimization techniques, including, but not limited to,rollout, inline optimization, etc.

Subsequent to generating the new modified code, that modified code iswritten to system memory and stored in memory locations that aredifferent from the memory locations of the application, STEP 1406.Further, page mappings are updated to make the modified code available,STEP 1408. This includes, for instance, indicating to the one or morecomponents of the computing environment, such as the operating system orthe MMU, as examples, of where the modified code is located, and thetype of access permitted for that code. For instance, the optimizerindicates that the modified code is located at physical memory regions xto x+n and should be made available at effective addresses y to y+n, andthe type of access is instruction fetch only which should be used inconjunction with an existing mapping for data accesses, either bychanging a current existing I/D translation memory region into aseparate I/D translation memory region in supplanting the pre-existingshared translation for addresses y to y+n by data translation to thepreviously used physical memory but limited to data only accesses inconjunction with instruction accesses for y to y+n being directed tophysical addresses x to x+n. In another aspect of at least oneembodiment, an instruction only translation is added to a pre-existingdata only translation. In one example, the optimizer is provided aninterface to facilitate providing this information.

In one embodiment, based on receiving the mapping information, theprocessor, such as the MMU, creates SLBEs to be used to translate to thenew pages on a control of system software extended to initializeseparate SLBE entries for instruction and data accesses, in accordancewith one aspect. For instance, the current SLBE that points to the codeprior to being modified is copied and the VSID is updated to reflect thelocation of the new pages and the NOA is set to instruction access only.Further, the NOA and the SLBE pointing to the unmodified code is updatedfrom shared to data access only. In particular, in one example, a newSLBE is created for instruction-only access and translated to a newvirtual address. Pages in the new virtual address range are initializedto the new supplied memory region. Pages within the new memory regionthat are not initialized to a new instruction-only page may beinitialized to point to the unmodified code pages when only a portion ofa memory region is modified. In one embodiment, these pages areinitialized when a new virtual address range in conjunction with aninstruction only SLBE is created. In another embodiment, they areinitialized in a deferred manner such that when an access is performed,a page fault is indicated and initialization occurs in conjunction withservicing the page fault.

Referring to FIG. 14B, in one example, optimization further takes intoaccount whether one or more extended mode controls are provided.Referring to FIG. 14B, the optimizer begins generating the optimizedcode, STEP 1450, and a determination is made as to whether the code isto benefit from extended mode features, INQUIRY 1452. If not, thencompliant code (i.e., code compliant with the currently activearchitecture level) is generated as described above, STEP 1454. However,if the determination is made that code is to benefit from extended modefeatures, then the code that is generated uses the one or moreadditional features that are available, based on selection by theoptimizer, STEP 1456. This includes, for instance, using an instructionthat replaces multiple instructions, using a higher architectural mode,or other types of enhancements. Further, one or more extended modecontrols are set by the optimizer for the application, STEP 1458. Forinstance, the optimizer injects code to enable extended mode featuresprior to use, as described with reference to FIG. 15, STEP 1460, oroptionally, performs steps to indicate the application or selectportions of the application (such as only DCO generated code) may useand/or is authorized to use, extended mode features, such as authorizethe application to use the extended mode features (e.g., set one or morecontrol indicators in PTE, requests that the extended mode controlauthorization facility be turned on, etc.), STEP 1462.

One example of injecting code to enable use of the extended modefeatures is described with reference to FIG. 15. FIG. 15 depicts oneexample flow of using a control register to enable extended modefeatures.

Initially, the unmodified application code is executing, STEP 1500, andthen a branch is performed to the optimized application code, STEP 1502.In one example, this includes executing an instruction fetch using anSLBE for instruction access only. At the new code, the optimizer setsthe extended mode control (e.g., extended mode enable facility) in acontrol register using, for instance, a series of instructions, STEP1504. For instance, a move from machine state register (mfmsr)instruction is used to take the contents of the MSR register and placethe MSR contents in a register, rx, (rx being an exemplary registerwherein x can take any register number, e.g., from 0 to 31 depending onthe registers provided in an architecture that may be used inconjunction with an architecture). Then, an OR immediate instruction isperformed to set the value to indicate extended mode is enabled. Then, amove to machine state register (mtmsr) instruction is performed to movethat value back to the machine state register. Optimized coding is thenperformed in the new mode, STEP 1506, i.e., using one or more extendedmode features, as deemed appropriate by the optimizer.

When processing is complete, then the extended mode control (e.g.,extended mode enable facility) is set to disabled by once again using anumber of instructions, STEP 1508. For instance, the mfmsr is executedand the value in the MSR is moved to a register, rx, an AND immediate isperformed to set the extended mode control to disabled, and that valueis moved to the MSR using, e.g., the mtmsr instruction. Then, processingreturns to the unoptimized original application code, STEP 1510. In oneexample, this includes using a branch to a special purpose register,such as a target address register (TAR). To perform this branch, thereturn address is loaded in a register rx (rx being an exemplaryregister wherein x can take any register number, e.g., from 0 to 31depending on the registers provided in an architecture that may be usedin conjunction with an architecture, and the value “return address”being represented either as an immediately loaded value, or a valueloaded from memory as an operand using one from a variety of possibleaddressing modes commonly used by load instructions in an architecture),a move to TAR instruction is executed to copy the value in rx to theTAR, and a branch conditional instruction is executed to branch to theaddress in the TAR. Processing then continues at the unmodifiedapplication code, STEP 1512.

In accordance to one embodiment, the TAR register is a target addressregister that may be used in conjunction with branch instructions as aregister-specified target address. In accordance with at least oneembodiment, the use of the TAR register is restricted to DCO functionsand other system functions and not available to unoptimized applicationcode. In one embodiment, the TAR register represents an exemplaryextended mode function that is used by a DCO component to generateoptimized code for branching to unoptimized code.

In one embodiment, for STEPs 1504 and 1508, instead of using a pluralityof instructions, a new instruction may be created, referred to, forinstance, as MTEM (Move to Extended Mode), that sets/resets an extendedmode control in a control register.

Further, in the example described above, one extended mode control isenabled allowing the application access to the extended mode features.However, in other embodiments, separate controls in the control registerand/or elsewhere may be enabled/disabled for individual features. Othervariations are also possible.

One example of a move from machine state register instruction isdescribed with reference to FIG. 16A. In one example format, a move frommachine state register instruction 1600 includes a plurality of opcodefields 1602 a, 1602 b indicating a move from machine state registeroperation, and a register field (RT) 1604. The contents of the MSR areplaced in the register designated in the RT field 1604.

Further, one example of a move to machine state register instruction isdescribed with reference to FIG. 16B. In one example format, a move frommachine state register instruction 1650 includes a plurality of opcodefields 1652 a, 1652 b indicating a move to machine state registeroperation, a register field (RS) 1654, and an L field 1656.

In operation, if L=0 then

-   -   MSR₄₈←(RS)₄₈|(RS)₄₉    -   MSR₅₈←(RS)₅₈|(RS)₄₉    -   MSR₅₉←(RS)₅₉|(RS)₄₉    -   MSR_(32:47 49:50 52:57 60:62)←(RS)_(32:47 49:50 52:57 60:62)

else

-   -   MSR₄₈ ₆₂←(RS)₄₈ ₆₂

The MSR is set based on the contents of register RS and of the L field.

L=0:

-   -   The result of ORing bits 48 and 49 of register RS is placed into        MSR₄₈. The result of ORing bits 58 and 49 of register RS is        placed into MSR₅₈. The result of ORing bits 59 and 49 of        register RS is placed into MSR₅₉. Bits 32:47, 49:50, 52:57, and        60:62 of register RS are placed into the corresponding bits of        the MSR.

L=1:

-   -   Bits 48 and 62 of register RS are placed into the corresponding        bits of the MSR. The remaining bits of the MSR are unchanged.

If L=0 this instruction is context synchronizing. If L=1 thisinstruction is execution synchronizing.

Described above is a facility in which an optimizer may provide anapplication with extended mode features (also referred to as enhanced orspecial modes.) In one aspect, a user level application starts with,e.g., MSR bits enabling such extended mode features as disabled. Theextended mode control bit (or bits) are not enabled to be set by anapplication level program, and no supervisor software interface isprovided to normal applications to enable these settings. Thus, anapplication attempting to use such instructions will experience an errorcorresponding to the execution of an illegal instruction. Then, when thedynamic optimizer generates and injects optimized code, the dynamicoptimizer enables the additional features for an application/addressspace, either by way of special permissions given by hardware to a DCOcomponent (e.g., a separate execution privilege level), or by aninterface between the DCO component and supervisor software to enablethese MSR controls and keep them set for the present application. Oncethis bit, or a plurality of bits to control separately differentcapabilities and modes, are set, the functions are available to theapplication, and maintained set for the application during task switchesperformed by the operating system, etc.

Additional MSR bits may also be provided to enable operational modes,such as FPU, VEC or VSX, while these are ostensibly disabled for aspecific application.

In one embodiment, the extended mode control bit, or an additional bitalso controls a branch and switch mode instruction which may be providedby the hardware to enable a DCO component to transfer control fromoriginal code to an optimized dynamically generated version of the codehaving been compiled to optimize a hot spot and take advantage of suchhigh performance mode instructions or resources—branch and switch modeto X—and a second branch instruction—branch and switch mode from X,where X corresponds to a specific of one or more modes including normalmode, and at least one extended mode.

In another aspect, as described herein, enablement bits are notassociated with an executing application by way of MSR bits, but are setat an application level. In conjunction with one embodiment, a pagetable entry contains one or more extended mode control bits associatedto a page. When the DCO component generates optimized code and installsa new page with such code, it causes the permissions of the page tableentry to be set to enable additional instructions, resources, or ISAlevels exceeding the ISA level set by the processor compatibilityregister PCR in accordance with the specification of the Power ISAv2.07, included herein by reference, or the VAL specification inaccordance with the System z/Architecture, included herein by reference,or any other software control for setting software-controlledarchitecture levels in accordance with an architecture. In anotheraspect of page table entry associated extended mode bits, the mode bitselects an alternate execution mode, such as a VLIW (Very LongInstruction Word) or WW-Power instruction set encoding.

In one aspect, a processor includes an instruction state context (ISC),such that the ISC indicates an architecture level of an instruction setarchitecture (ISA being used). Thus, an application program may specifyan ISA to be used for a portion of the program currently being executed,by specifying the ISC.

In addition to the above, in a further aspect, a capability is providedto enable a partition that includes one or more applications that use orare capable of using extended mode features to be migrated to anotherhost. To facilitate this migration, various steps are taken to ensurethat the partition may be successfully moved, especially whenapplications executing within the partition are enhanced with extendedmode features.

One step to facilitate migration of a partition includes registering useof the extended mode facility by the optimizer, such that the operatingsystem and/or hypervisor are aware of which applications, and therefore,which partitions are partaking in the extended mode facility. Thus, inone aspect, when new ISA capabilities are used by the optimizer orextended modes that may not be available on other models, and the codegenerated by the optimizer is generated in a partition otherwise set tocompatibility with an older ISA version, the optimizer registers that itis using potentially non-migratable capabilities. In another aspect,when extended mode features, instructions and resources are used whichare not available on all systems, but the code is generated in apartition that is migratable, the optimizer also registers that is usingpotentially non-migratable capabilities. In one example, the registeringis accomplished via interacting with supervisor software, such as theoperating system or hypervisor.

One embodiment of logic to perform registration is described withreference to FIG. 17. This logic is performed, for instance, by theoptimizer the first time that it wishes to use the extended modefacility.

Referring to FIG. 17, initially, the optimizer determines, based on, forinstance, analysis of the applications it is optimizing and thepotential extended mode features available, whether the use of theextended mode facility would be beneficial, INQUIRY 1700. If it isdetermined that use of the extended mode facility is not beneficial,then the optimizer uses the current level of the architected ISA ingenerating optimized code, STEP 1702. Otherwise, if the optimizerdetermines that use of the extended mode facility may be beneficial,INQUIRY 1700, then a further determination is made as to whether theextended mode facility is already enabled for the optimizer, i.e., hasthe optimizer already registered for the extended mode facility, INQUIRY1704. If the optimizer has already registered, then the optimizer mayuse one or more features of the extended mode facility, STEP 1710.

However, if the optimizer has not already registered for the extendedmode facility, INQUIRY 1704, then the optimizer requests use of theextended mode facility, STEP 1706, and registers such use, STEP 1708. Inone example, the request to use and the register to use may be combinedinto one supervisory call. In one particular example, the supervisorycall is from the optimizer to the operating system, and then theoperating system registers with the hypervisor. In another example, theoptimizer may be able to directly communicate the request to thehypervisor (e.g., the optimizer has been authorized to communicate withthe hypervisor). Subsequent to registration, the optimizer may use oneor more features of the extended mode facility, STEP 1710.

In one embodiment, to use the one or more features of the extended modefacility, the optimizer generates code and includes one or more of theextended mode features within the optimized code. In particular, theoptimizer makes a copy of the original code to be modified, creates themodified code, and places a transfer, such as a branch in the copiedoriginal code to the modified code, as shown in FIG. 18.

Referring to FIG. 18, an application 1800 includes for instance, aplurality of code regions, including a first region 1802, which is basedon, for instance, a first architectural level (e.g., Power 7), and twooptimized regions, created by the optimizer, including region 1804 thatwas compiled by an optimizer (e.g., dynamic optimizer component) usinginstructions from a different architectural level (e.g., an enhancedlevel, Power 8), and another region 1806 that was compiled usingmillicode instructions not typically available to the application.Branches are placed in application 1802 to both regions 1804 and 1806(e.g., b opt_frag1, b opt_frag2, respectively), and from the regionsback to the unoptimized portion of the code (e.g., btar—branch to targetaddress register).

For instance, in one embodiment, the branch distance between theoriginal code and the optimized code are long distances and the branchis performed using a special purpose register exclusively for use by theoptimizer (e.g., a target address register). In one embodiment,transfers from the patched original code occur by branches that enablenew high performance modes (or other modes used by the optimized codebut not the application outside of the optimized code), and transfersback to the original code uses branches that disable new highperformance modes (or other modes used by the optimized code but not theapplication outside of the optimized code) and restore the applicationmode previously enforced.

Applications, such as the application depicted in FIG. 18, may beexecuting in a partition that is to be migrated from one host to anotherhost (e.g., system, machine, etc.). When a partition is to move from onehost to another host, the hypervisor, in one example, determines whetherthe target machine can support the extended mode features used by theoptimized code. For instance, referring to FIGS. 19A-19C, assume that apartition 1902 (FIG. 19B) is executing on a system 1900, which is at anarchitectural level of, for instance, Power 8. Also assume that thepartition includes optimized code that includes millicode instructions1906 based on, for instance, Power 8, and code that uses architecturalfeatures 1908 of, for instance, Power 8. The hypervisor determines thatpartition 1902 can be migrated to system 1920 (FIG. 19A), if themillicode instructions 1906 are removed, since these instructions arenot supported by the Power 9 system. However, the code using thearchitected features 1908 are supported, since Power 9 subsumes thisarchitectural level.

Similarly, the hypervisor determines that the partition could bemigrated to system 1930 (FIG. 19C) only if both the millicodeinstructions 1906 and the architected features 1908 are removed, sinceneither are supported by a system that is at an architectural level of,for instance, Power 7.

In one particular embodiment, when a partition is to move from one hostto another host (e.g., one machine to another machine, one system toanother system, etc.), the hypervisor, in one example, performs adetermination as to whether the optimizer has registered the use ofextended mode features. If so, the hypervisor determines thecapabilities of the target machine to determine whether the targetmachine can support the features used by the optimized code. If thetarget machine can support the extended mode features used by theoptimized code, then the partition is migrated. Otherwise, in oneembodiment, the operating system is notified.

The operating system, in one specific example, enumerates all of theprocesses within the partition that use the capabilities exceeding thetarget machine level, and notifies the optimizer associated with thoseprocesses that the partition is to be migrated to a machine that doesnot support the extended mode features. In one example, thisnotification is via a callback from the operating system to theoptimizer. The callback may include an indication of what features aresupported. In accordance with one embodiment, a callback corresponds toa known address provided by an optimizer to another component, such asan operating system, at which to start execution when a certaincondition occurs. Responsive to determining a callback is needed, theoperating system starts executing the optimizer to be called back upon,and initializes the program counter with the value of the call backaddress. In one embodiment, the callback is implemented as a signal inaccordance with the POSIX standard.

Further details regarding preparing to migrate a partition, includingproviding such a notification, are described with reference to FIG. 20.Referring to FIG. 20, in one embodiment, the hypervisor determineswhether the partition to be migrated is using any extended modefacilities, STEP 2000. This determination may be made, for instance,based on previous registrations that indicate what facilities are beingused. If it is determined that the partition is not using any extendedmode facilities, then migration begins, assuming any other conditionsfor migration have been met, STEP 2002. However, if it is determinedthat the partition may be using extended mode facilities, then thehypervisor obtains an indication of what specific extended modefacilities may be being used in the partition, STEP 2004. Further, thehypervisor obtains an indication of the capabilities of the targetsystem, STEP 2006. In one example, the hypervisor may obtain this from alist of capabilities that is maintained by the target system.

A determination is made as to whether the extended mode facilities ofthe partition are supported by the target machine, INQUIRY 2008. Thismay be determined by, for instance, comparing the indication of extendedmode features obtained in STEP 2004 with the indication of supportedfacilities obtained in STEP 2006. In one particular example, if themigrating partition includes code that has an ISA level less than theISA level of the target machine, then the target machine supports theextended mode features of an enhanced ISA. Further, if the partitionuses code enhancements, such as millicode features, and the code withthese features can execute correctly on the target machine, then thetarget machine supports those features. Other examples also exist. Ifthe extended mode facilities of the migrating partition are supported bythe target machine, then the migration continues, STEP 2010.

Returning to INQUIRY 2008, if the target machine does not support one ormore of the extended mode features of the partition, then the hypervisornotifies the operating system of an impending migration and requeststhat steps be taken to make the partition migratable, STEP 2012. In oneexample, the hypervisor notifies the operating system by initiating acall back. For instance, a call back interface (i.e., an interface wherethe hypervisor/supervisory software can send an unsolicited indication)is used, which is implemented, for instance, as an exception.

Based on that request, the operating system takes steps to have theextended mode facilities removed, or at least those that are notsupported by the target system, STEP 2014. For instance, the operatingsystem notifies the optimizer and based on the notification, theoptimizer invalidates optimizer generated code that includes theextended mode features. In one embodiment, all optimizer generated codeof a process within the partition is invalidated, if that code includesany extended mode features. In a further embodiment, however, only codeportions (e.g., code regions, code segments, code pages) containingextended mode features are invalidated.

In one or more embodiments, applications continue executing until asuitable transition point where control can be transferred fromgenerated code using extended mode features, when the locus of controlis currently in optimizer generated code containing extended modefeatures. In one embodiment, code is generated to limit the duration ofexecution until such a point is reached. At suitable transition points,in one example, polling sequences (optionally a single optimizedinstruction) perform polling if a request to invalidate the current codefragment is pending, and pass control to the optimizer if adetermination is successful.

In another example, rollback to a previous snapshot or checkpoint isused. This snapshot is generated, for instance, using transactionalexecution techniques. In accordance with one embodiment, all optimizedfragments are embedded in a transaction, such that a rollback can beperformed to the beginning of each fragment, the beginning of thefragment corresponding to an address in the unmodified code.

When all code exceeding the target machine capabilities has been flushed(i.e., removed from the system), the operating system is notified. Then,when the operating system has received notification from all processes,the hypervisor is notified. The hypervisor then initiates migration. If,in one example, an optimizer is unresponsive to an operating systemcallback to flush, the operating system terminates the application.

Based on the callback and flushing, the optimizer may generate new codethat is compatible with the target system prior to migration. In anotherembodiment, the new code is not generated until after migration.

Although in the description herein, the hypervisor, operating system andoptimizer perform certain tasks, in other embodiments, the tasks may beperformed by other of the components. For instance, the operating systemmay perform the tasks of the hypervisor, or other supervisory componentsmay be used. Further, the optimizer, if authorized, may perform one ormore of the tasks of the operating system, etc.

Further details regarding notification to the optimizer and steps to beperformed based on the notification are described with reference to FIG.21. Initially, in one embodiment, the operating system (or anothersupervisory component) checks whether any optimized processes are usingany of the extended mode features, INQUIRY 2100. For example, if the oneor more applications of a partition having been optimized to useextended code have terminated, no processes are currently using extendedmode features. If it is determined by the operating system that theoptimized processes are not using extended mode features, then theoperating system notifies the hypervisor that migration may proceed,STEP 2102.

Returning to INQUIRY 2100, if, however, the operating system determinesthat the optimized processes are using one or more extended modefeatures, then the operating system notifies the optimizer of themigration and loss of the ability to use such features, STEP 2104. Inone example, this notification includes an indication of thearchitectural level (ISA level) supported by the target system and/orthe particular extended mode features that are supported.

Based on receiving this notification, the optimizer is to take action,such as remove the invalidated code. The optimizer has, for instance, atime window in which to take this action and report back to theoperating system. The time window is set, in one example, by anadministrator based, e.g., on the reason for migration, such as anemergency situation due to system failure or some other reason, orplanned maintenance. A determination is made as to whether the optimizerperformed the action and reported back to the operating system withinthe acceptable time frame, INQUIRY 2106.

If the optimizer did report success to the operating system within theacceptable time frame, processing proceeds with migrating the partition,STEP 2108. This includes, for instance, checking whether there are moreoptimized processes using one or more extended mode features, INQUIRY2110. If there are more processes, then processing continues at STEP2104. Otherwise, the operating system reports to the hypervisor toproceed with migration, STEP 2112.

Returning to INQUIRY 2106, if the operating system did not receivetimely notification from the optimizer, then a further determination ismade, based for instance on an administrative parameter, whether themigration is to be cancelled or the application is to be terminated,INQUIRY 2114.

Based on a determination that the migration is to be cancelled, theoperating system informs the hypervisor of such, STEP 2116. Otherwise,based on a determination that the application is to be terminated, theapplication is terminated, STEP 2118, and processing continues with STEP2110.

Although the above processing depicts serial processing for theindividual processes, in other embodiments, the processes may beprocessed in parallel.

As indicated above, responsive to the optimizer receiving notificationthat optimized code has to be invalidated, the optimizer invalidatescode generated by the optimizer. A number of invalidation strategies maybe performed. For instance, all optimizer generated code of a process isinvalidated, if any of the code has been generated using extended modefeatures. In another embodiment, only code portions that includeextended mode features are invalidated. Further details regardinginvalidating optimized code by an optimizer are described with referenceto FIG. 22.

Referring to FIG. 22, in this embodiment, it is assumed that there is anarbitrary point in the optimized code in which to transition from theoptimized code to the unoptimized code. Initially, in one embodiment,the optimizer receives notification to invalidate (e.g., drop, remove,flush) the code that includes the extended mode features, STEP 2200. Theoptimizer then checks whether the application is currently executingnative (unoptimized) code or optimized code, INQUIRY 2202. In oneembodiment, this is determined based on the value of the programcounter. For instance, the value of the program counter indicateswhether the application is processing in optimized or unoptimized code.

Based on determining that the application is executing in native code(i.e., it is executing in an unoptimized code region), the optimizedcode or at least those portions that include the unsupported extendedmode features may be removed, STEP 2204. When this is complete, theoptimizer notifies the operating system, STEP 2206, and applicationexecution continues, STEP 2208.

Returning to INQUIRY 2202, if it is determined that the application iscurrently executing in optimized code, then a further check is made asto whether the application is currently executing code that includesextended mode features not supported by the target system, INQUIRY 2210.If the application is currently executing in code using only extendedmode features supported by the target system, STEP 2212, then theoptimizer flushes all the optimized code containing features above thetarget level, STEP 2214, and reports success to the operating system,STEP 2216. The application continues to execute, STEP 2218.

However, if the application is currently executing code using extendedmode features not available on the target system, INQUIRY 2210, then thenative state is materialized at a clean cut-over point in theapplication, STEP 2220. This may be performed using, for instance, statere-materialization or rollback, as examples. In one embodiment inaccordance with state re-materialization, the dynamic optimizer is ableto materialize the full state corresponding to a suitable unoptimizedprogram location at defined (and optionally, all) points of theoptimized code. In one example, the state materialization uses anapproach in which enough state is maintained to re-compute the processorstate when an unpredicted event, such as a signal (synchronousexception), or a switch from optimized code to unoptimized code may makeotherwise unused processor state visible. State materializationtechniques are known and one example is described in M. Gschwind, E. R.Altman, Precise Exception Semantics in Dynamic Optimization 2002Symposium on Compiler Construction (CC 2002), Grenoble, France, April2002, which is hereby incorporated by reference herein in its entirety.

In accordance with one embodiment based on rolling back state updates ofa partially executed optimized code, the optimized code is embeddedwithin a transaction, and when a suitable in-order state is required,and the unoptimized program state is to be generated, a rollback of allupdates of the present optimized code fragment rolls back execution tothe point at which the optimized code fragment was entered,corresponding to an exemplary state where the transfer to optimized codewith extended mode usage occurred.

Further, the program counter is set to the cut-over point in the nativeexecutable code, i.e., to the value of the instruction address of theunmodified code corresponding to the state of the state having beengenerated. In at least one embodiment, execution continues with theunmodified code when the code using extended mode instructions subjectto flushing has been flushed, STEP 2222.

Additionally, the optimized code is flushed, STEP 2224. For instance,either all of the optimized code or the code portions including theunsupported external mode features is flushed. Flushing can be performedin a number of ways, including, for instance: removing all the branchesfrom the native code to the optimized code; invalidating modified nativecode pages in memory that include branches from the native code to theoptimized code and force a demand load from the binary (e.g., get a pagefault); or remove code pages and replace them with pages full of trapinstructions, either by writing into existing pages, or by modifyingpage translations to point to one page with trap instructions.Completion of the flushing is reported to the operating system, STEP2226, and the application continues to execute from the newly computedprogram counter, STEP 2228.

Another embodiment of logic to invalidate optimized code by an optimizeris described with reference to FIG. 23. In this embodiment, it isassumed that there is no arbitrary point in the optimized code in whichto transition from the optimized code to the unoptimized code.

Referring to FIG. 23, initially, in one embodiment, the optimizerreceives notification to invalidate (e.g., drop, remove, flush) the codethat includes the extended mode features, STEP 2300. The optimizer thenchecks whether the application is currently executing native code oroptimized code, INQUIRY 2302. Based on determining that the applicationis executing in native mode (i.e., it is executing in an unoptimizedcode region), the optimized code or at least those portions that includethe unsupported extended mode features may be removed, STEP 2304. Whenthis is complete, the optimizer notifies the operating system, STEP2306, and application execution continues, STEP 2308.

Returning to INQUIRY 2302, if it is determined that the application iscurrently executing in optimized code, then a further check is made asto whether the application is currently executing code that includesextended mode features not supported by the target system, INQUIRY 2310.If the application is currently executing in code using only extendedmode features supported by the target system, STEP 2312, then theoptimizer flushes all the optimized code containing features above thetarget level, STEP 2314, and reports success to the operating system,STEP 2316. The application continues to execute, STEP 2318.

However, if the application is currently executing code using extendedmode features not available on the target system, INQUIRY 2310, then inthis embodiment, processing waits for a suitable checkpoint, STEP 2320.For instance, one or more checkpoints are built into the code to providea point in which a transition to unoptimized code may be performed. Whena suitable checkpoint is reached, native state is materialized at aclean cut-over point in the application, STEP 2322. This may beperformed using, for instance, state re-materialization or rollback, asexamples. Further, the program counter is set to the cut-over point inthe native executable code, STEP 2324. Additionally, the optimized codeis flushed, STEP 2326. For instance, either all of the optimized code orthe code portions including the unsupported external mode features areflushed.

Completion of the flushing is reported to the operating system, STEP2328, and the application continues to execute from the newly computedprogram counter, STEP 2330.

As described above, it is beneficial to have suitable cut-over points totransition between optimized and unoptimized code. Examples of suitablecut-over points are depicted in FIG. 24. In this example, unoptimizedcode 2400 has branches to optimized code 2402, and vice versa. Thesebranches provide suitable cut-over points. In particular, eachinstruction marked with an address (a_) in the figure indicates acut-over point that may be used. In one example, the optimizer may gaincontrol at the indicated points by, for instance, placing traps onbranches into optimized groups (e.g., a1, a3, and a5), traps on branchesbetween optimized groups (e.g., a5), and traps on btar (branch to targetaddress register) (e.g., a2, a5, a6).

In one example, to raise a branch on a btar, an instruction match isused in which a register is used for matching instruction words. Inanother example, a control register is operably linked to hardware thatdetects and executes btar. Other types of branches may also be used inwhich, for instance, a new type of branch or new branch field may be setto trigger trap or be matched by instruction words.

Checkpoints may also be added to long running loops in order to providea point in which the optimizer might gain control.

In using a checkpoint in order to gain control at a specific point, acheckpoint is inserted in the code, and a checkpoint instruction tests aflag (e.g., in a control register (such as MSR, PSW) or in memory), andif the flag is true, then branch to the checkpoint. Example checkpointinstructions include: if (memory_flag) then goto checkpoint; LT (loadand test) r2, mem; BZ (branch zero) checkpoint_found.

Described above is a partition mobility facility (e.g., a live partitionmobility facility) that enables a partition to be moved from one host toanother host, even if the partition includes extended mode features. Inone embodiment, the target system is notified that a partition withextended mode facilities is being moved to the target system. The sourcesystem (the system from which the partition is being moved) indicatesextended facilities are being used by the partition, and the targetsystem receives an extended facility list, in one example. Further, inone embodiment, if pages are marked with additional authority/facilityindications, these indications are provided to the target system. On thetarget system, indications for each page are mapped to correspondingindications on the target system, and stored, for instance, inassociated page table entries (or other address translation structures).

In one aspect, a supervisory component, such as a hypervisor, supportslive partition mobility. An optimizer enables extended mode features,registers the use of the extended mode features with the supervisorycomponent, and receives callbacks when a partition migration isimpending.

In one embodiment, based on the callback, the optimizer flushes(invalidates) optimized generated code. The flushing includes, forinstance, allowing the application to continue execution to a suitabletransition point to unoptimized code.

In one embodiment, the code generated by the optimizer is generated in amanner such that suitable transition points are inserted and identifiedin the generated code. Further, in one embodiment, an indicatorinstruction is configured to poll for a callback event and transfercontrol to the optimizer. In a further embodiment, the flushing involvesrolling back to a checkpoint. The code is generated by the optimizer, inone embodiment, in a manner such that suitable rollback points aregenerated (e.g., including the use of transactions).

In a further embodiment, a determination is made that live partitionmigration is to be performed, a target machine is determined, the levelof extended modes supported by the target machine is determined, and adetermination is made based on the target machine's supported enhancedfeatures of whether the dynamically generated code can be moved to thetarget machine.

In one example, when there is a negative determination, the codegenerated by the optimizer is not available causing the code cache to becleared. In one example, the clearing is performed using a callback tothe optimizer component. In a further embodiment, the clearing isinitiated on the source machine and the code generation is one ofrestricted to the common target level and/or suppressed until completionof the migration.

Referring to FIG. 25, in one example, a computer program product 2500includes, for instance, one or more non-transitory computer readablestorage media 2502 to store computer readable program code means, logicand/or instructions 2504 thereon to provide and facilitate one or moreembodiments.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

In addition to the above, one or more aspects may be provided, offered,deployed, managed, serviced, etc. by a service provider who offersmanagement of customer environments. For instance, the service providercan create, maintain, support, etc. computer code and/or a computerinfrastructure that performs one or more aspects for one or morecustomers. In return, the service provider may receive payment from thecustomer under a subscription and/or fee agreement, as examples.Additionally or alternatively, the service provider may receive paymentfrom the sale of advertising content to one or more third parties.

In one aspect, an application may be deployed for performing one or moreembodiments. As one example, the deploying of an application comprisesproviding computer infrastructure operable to perform one or moreembodiments.

As a further aspect, a computing infrastructure may be deployedcomprising integrating computer readable code into a computing system,in which the code in combination with the computing system is capable ofperforming one or more embodiments.

As yet a further aspect, a process for integrating computinginfrastructure comprising integrating computer readable code into acomputer system may be provided. The computer system comprises acomputer readable medium, in which the computer medium comprises one ormore embodiments. The code in combination with the computer system iscapable of performing one or more embodiments.

Although various embodiments are described above, these are onlyexamples. For example, computing environments of other architectures canbe used to incorporate and use one or more embodiments. Further,different instructions, instruction formats, instruction fields and/orinstruction values may be used. Yet further, other types of addresstranslation may benefit from one or more aspects. Many variations arepossible.

Further, other types of computing environments can benefit and be used.As an example, a data processing system suitable for storing and/orexecuting program code is usable that includes at least two processorscoupled directly or indirectly to memory elements through a system bus.The memory elements include, for instance, local memory employed duringactual execution of the program code, bulk storage, and cache memorywhich provide temporary storage of at least some program code in orderto reduce the number of times code must be retrieved from bulk storageduring execution.

Input/Output or I/O devices (including, but not limited to, keyboards,displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives andother memory media, etc.) can be coupled to the system either directlyor through intervening I/O controllers. Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodems, and Ethernet cards are just a few of the available types ofnetwork adapters.

Referring to FIG. 26, representative components of a Host Computersystem 5000 to implement one or more embodiments are portrayed. Therepresentative host computer 5000 comprises one or more CPUs 5001 incommunication with computer memory (i.e., central storage) 5002, as wellas I/O interfaces to storage media devices 5011 and networks 5010 forcommunicating with other computers or SANs and the like. The CPU 5001 iscompliant with an architecture having an architected instruction set andarchitected functionality. The CPU 5001 may have access registertranslation (ART) 5012, which includes an ART lookaside buffer (ALB)5013, for selecting an address space to be used by dynamic addresstranslation (DAT) 5003 for transforming program addresses (virtualaddresses) into real addresses of memory. A DAT typically includes atranslation lookaside buffer (TLB) 5007 for caching translations so thatlater accesses to the block of computer memory 5002 do not require thedelay of address translation. Typically, a cache 5009 is employedbetween computer memory 5002 and the processor 5001. The cache 5009 maybe hierarchical having a large cache available to more than one CPU andsmaller, faster (lower level) caches between the large cache and eachCPU. In some implementations, the lower level caches are split toprovide separate low level caches for instruction fetching and dataaccesses.

In one embodiment, an instruction is fetched from memory 5002 by aninstruction fetch unit 5004 via a cache 5009. The instruction is decodedin an instruction decode unit 5006 and dispatched (with otherinstructions in some embodiments) to instruction execution unit or units5008. Typically several execution units 5008 are employed, for examplean arithmetic execution unit, a floating point execution unit and abranch instruction execution unit. The instruction is executed by theexecution unit, accessing operands from instruction specified registersor memory as needed. If an operand is to be accessed (loaded or stored)from memory 5002, a load/store unit 5005 typically handles the accessunder control of the instruction being executed. Instructions may beexecuted in hardware circuits or in internal microcode (firmware) or bya combination of both.

As noted, a computer system includes information in local (or main)storage, as well as addressing, protection, and reference and changerecording. Some aspects of addressing include the format of addresses,the concept of address spaces, the various types of addresses, and themanner in which one type of address is translated to another type ofaddress. Some of main storage includes permanently assigned storagelocations. Main storage provides the system with directly addressablefast-access storage of data. Both data and programs are to be loadedinto main storage (from input devices) before they can be processed.

Main storage may include one or more smaller, faster-access bufferstorages, sometimes called caches. A cache is typically physicallyassociated with a CPU or an I/O processor. The effects, except onperformance, of the physical construction and use of distinct storagemedia are generally not observable by the program.

Separate caches may be maintained for instructions and for dataoperands. Information within a cache is maintained in contiguous byteson an integral boundary called a cache block or cache line (or line, forshort). A model may provide an EXTRACT CACHE ATTRIBUTE instruction whichreturns the size of a cache line in bytes. In another embodiment, thisinformation may be obtained from firmware, e.g., in accordance withinterfaces specified by the Power Architecture Platform Referencespecification. A model may also provide one or more of data cache blocktouch (dcbt), PREFETCH DATA and PREFETCH DATA RELATIVE LONG instructionswhich effects the prefetching of storage into the data or instructioncache or the releasing of data from the cache.

Storage is viewed as a long horizontal string of bits. For mostoperations, accesses to storage proceed in a left-to-right sequence. Thestring of bits is subdivided into units of eight bits. An eight-bit unitis called a byte, which is the basic building block of all informationformats. Each byte location in storage is identified by a uniquenonnegative integer, which is the address of that byte location or,simply, the byte address. Adjacent byte locations have consecutiveaddresses, starting with 0 on the left and proceeding in a left-to-rightsequence. Addresses are unsigned binary integers and are 24, 31, or 64bits.

Information is transmitted between storage and a CPU or a channelsubsystem one byte, or a group of bytes, at a time. Unless otherwisespecified, in, for instance, the POWER ISA and z/Architecture, a groupof bytes in storage is addressed by the leftmost byte of the group. Thenumber of bytes in the group is either implied or explicitly specifiedby the operation to be performed. When used in a CPU operation, a groupof bytes is called a field. Within each group of bytes, in, forinstance, the POWER ISA and z/Architecture, bits are numbered in aleft-to-right sequence. In the POWER ISA and z/Architecture, theleftmost bits are sometimes referred to as the “high-order” bits and therightmost bits as the “low-order” bits. Bit numbers are not storageaddresses, however. Only bytes can be addressed. To operate onindividual bits of a byte in storage, the entire byte is accessed. Thebits in a byte are numbered 0 through 7, from left to right (in, e.g.,the z/Architecture). The bits in an address may be numbered 8-31 or40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bit addresses; theyare numbered 0-63 for 64-bit addresses. In one example, bits 8-31 and1-31 apply to addresses that are in a location (e.g., register) that is32 bits wide, whereas bits 40-63 and 33-63 apply to addresses that arein a 64-bit wide location. Within any other fixed-length format ofmultiple bytes, the bits making up the format are consecutively numberedstarting from 0. For purposes of error detection, and in preferably forcorrection, one or more check bits may be transmitted with each byte orwith a group of bytes. Such check bits are generated automatically bythe machine and cannot be directly controlled by the program. Storagecapacities are expressed in number of bytes. When the length of astorage-operand field is implied by the operation code of aninstruction, the field is said to have a fixed length, which can be one,two, four, eight, or sixteen bytes. Larger fields may be implied forsome instructions. When the length of a storage-operand field is notimplied but is stated explicitly, the field is said to have a variablelength. Variable-length operands can vary in length by increments of onebyte (or with some instructions, in multiples of two bytes or othermultiples). When information is placed in storage, the contents of onlythose byte locations are replaced that are included in the designatedfield, even though the width of the physical path to storage may begreater than the length of the field being stored.

Certain units of information are to be on an integral boundary instorage. A boundary is called integral for a unit of information whenits storage address is a multiple of the length of the unit in bytes.Special names are given to fields of 2, 4, 8, 16, and 32 bytes on anintegral boundary. A halfword is a group of two consecutive bytes on atwo-byte boundary and is the basic building block of instructions. Aword is a group of four consecutive bytes on a four-byte boundary. Adoubleword is a group of eight consecutive bytes on an eight-byteboundary. A quadword is a group of 16 consecutive bytes on a 16-byteboundary. An octoword is a group of 32 consecutive bytes on a 32-byteboundary. When storage addresses designate halfwords, words,doublewords, quadwords, and octowords, the binary representation of theaddress contains one, two, three, four, or five rightmost zero bits,respectively. Instructions are to be on two-byte integral boundaries.The storage operands of most instructions do not have boundary-alignmentrequirements.

On devices that implement separate caches for instructions and dataoperands, a significant delay may be experienced if the program storesinto a cache line from which instructions are subsequently fetched,regardless of whether the store alters the instructions that aresubsequently fetched.

In one example, the embodiment may be practiced by software (sometimesreferred to licensed internal code, firmware, micro-code, milli-code,pico-code and the like, any of which would be consistent with one ormore embodiments). Referring to FIG. 26, software program code whichembodies one or more aspects may be accessed by processor 5001 of thehost system 5000 from long-term storage media devices 5011, such as aCD-ROM drive, tape drive or hard drive. The software program code may beembodied on any of a variety of known media for use with a dataprocessing system, such as a diskette, hard drive, or CD-ROM. The codemay be distributed on such media, or may be distributed to users fromcomputer memory 5002 or storage of one computer system over a network5010 to other computer systems for use by users of such other systems.

The software program code includes an operating system which controlsthe function and interaction of the various computer components and oneor more application programs. Program code is normally paged fromstorage media device 5011 to the relatively higher-speed computerstorage 5002 where it is available for processing by processor 5001. Thetechniques and methods for embodying software program code in memory, onphysical media, and/or distributing software code via networks are wellknown and will not be further discussed herein. Program code, whencreated and stored on a tangible medium (including but not limited toelectronic memory modules (RAM), flash memory, Compact Discs (CDs),DVDs, Magnetic Tape and the like is often referred to as a “computerprogram product”. The computer program product medium is typicallyreadable by a processing circuit preferably in a computer system forexecution by the processing circuit.

FIG. 27 illustrates a representative workstation or server hardwaresystem in which one or more embodiments may be practiced. The system5020 of FIG. 27 comprises a representative base computer system 5021,such as a personal computer, a workstation or a server, includingoptional peripheral devices. The base computer system 5021 includes oneor more processors 5026 and a bus employed to connect and enablecommunication between the processor(s) 5026 and the other components ofthe system 5021 in accordance with known techniques. The bus connectsthe processor 5026 to memory 5025 and long-term storage 5027 which caninclude a hard drive (including any of magnetic media, CD, DVD and FlashMemory for example) or a tape drive for example. The system 5021 mightalso include a user interface adapter, which connects the microprocessor5026 via the bus to one or more interface devices, such as a keyboard5024, a mouse 5023, a printer/scanner 5030 and/or other interfacedevices, which can be any user interface device, such as a touchsensitive screen, digitized entry pad, etc. The bus also connects adisplay device 5022, such as an LCD screen or monitor, to themicroprocessor 5026 via a display adapter.

The system 5021 may communicate with other computers or networks ofcomputers by way of a network adapter capable of communicating 5028 witha network 5029. Example network adapters are communications channels,token ring, Ethernet or modems. Alternatively, the system 5021 maycommunicate using a wireless interface, such as a CDPD (cellular digitalpacket data) card. The system 5021 may be associated with such othercomputers in a Local Area Network (LAN) or a Wide Area Network (WAN), orthe system 5021 can be a client in a client/server arrangement withanother computer, etc. All of these configurations, as well as theappropriate communications hardware and software, are known in the art.

FIG. 28 illustrates a data processing network 5040 in which one or moreembodiments may be practiced. The data processing network 5040 mayinclude a plurality of individual networks, such as a wireless networkand a wired network, each of which may include a plurality of individualworkstations 5041, 5042, 5043, 5044. Additionally, as those skilled inthe art will appreciate, one or more LANs may be included, where a LANmay comprise a plurality of intelligent workstations coupled to a hostprocessor.

Still referring to FIG. 28, the networks may also include mainframecomputers or servers, such as a gateway computer (client server 5046) orapplication server (remote server 5048 which may access a datarepository and may also be accessed directly from a workstation 5045). Agateway computer 5046 serves as a point of entry into each individualnetwork. A gateway is needed when connecting one networking protocol toanother. The gateway 5046 may be preferably coupled to another network(the Internet 5047 for example) by means of a communications link. Thegateway 5046 may also be directly coupled to one or more workstations5041, 5042, 5043, 5044 using a communications link. The gateway computermay be implemented utilizing one of an IBM Power Systems server and anIBM System z server available from International Business MachinesCorporation.

Referring concurrently to FIG. 27 and FIG. 28, software programming code5031 which may embody one or more aspects may be accessed by theprocessor 5026 of the system 5020 from long-term storage media 5027,such as a CD-ROM drive or hard drive. The software programming code maybe embodied on any of a variety of known media for use with a dataprocessing system, such as a diskette, hard drive, or CD-ROM. The codemay be distributed on such media, or may be distributed to users 5050,5051 from the memory or storage of one computer system over a network toother computer systems for use by users of such other systems.

Alternatively, the programming code may be embodied in the memory 5025,and accessed by the processor 5026 using the processor bus. Suchprogramming code includes an operating system which controls thefunction and interaction of the various computer components and one ormore application programs 5032. Program code is normally paged fromstorage media 5027 to high-speed memory 5025 where it is available forprocessing by the processor 5026. The techniques and methods forembodying software programming code in memory, on physical media, and/ordistributing software code via networks are well known and will not befurther discussed herein. Program code, when created and stored on atangible medium (including but not limited to electronic memory modules(RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and thelike is often referred to as a “computer program product”. The computerprogram product medium is typically readable by a processing circuitpreferably in a computer system for execution by the processing circuit.

The cache that is most readily available to the processor (normallyfaster and smaller than other caches of the processor) is the lowest (L1or level one) cache and main store (main memory) is the highest levelcache (L3 if there are 3 levels). The lowest level cache is oftendivided into an instruction cache (I-Cache) holding machine instructionsto be executed and a data cache (D-Cache) holding data operands.

Referring to FIG. 29, an exemplary processor embodiment is depicted forprocessor 5026. Typically one or more levels of cache 5053 are employedto buffer memory blocks in order to improve processor performance. Thecache 5053 is a high speed buffer holding cache lines of memory datathat are likely to be used. Typical cache lines are 64, 128 or 256 bytesof memory data. Separate caches are often employed for cachinginstructions than for caching data. Cache coherence (synchronization ofcopies of lines in memory and the caches) is often provided by various“snoop” algorithms well known in the art. Main memory storage 5025 of aprocessor system is often referred to as a cache. In a processor systemhaving 4 levels of cache 5053, main storage 5025 is sometimes referredto as the level 5 (L5) cache since it is typically faster and only holdsa portion of the non-volatile storage (DASD, tape etc) that is availableto a computer system. Main storage 5025 “caches” pages of data paged inand out of the main storage 5025 by the operating system.

A program counter (instruction counter) 5061 keeps track of the addressof the current instruction to be executed. A program counter in az/Architecture processor is 64 bits and can be truncated to 31 or 24bits to support prior addressing limits. A program counter in a PowerArchitecture processor is 64 bits and can be truncated to 32 bits tosupport prior addressing limits. A program counter is typically embodiedin a PSW (program status word) of a computer such that it persistsduring context switching. Thus, a program in progress, having a programcounter value, may be interrupted by, for example, the operating system(context switch from the program environment to the operating systemenvironment). The PSW of the program maintains the program counter valuewhile the program is not active, and the program counter (in the PSW) ofthe operating system is used while the operating system is executing.Typically, the program counter is incremented by an amount equal to thenumber of bytes of the current instruction. RISC (Reduced InstructionSet Computing) instructions are typically fixed length while CISC(Complex Instruction Set Computing) instructions are typically variablelength. Instructions of the IBM z/Architecture are CISC instructionshaving a length of 2, 4 or 6 bytes. Instructions of the IBM Power ISAare RISC instructions having a length of 4 bytes. The Program counter5061 is modified by either a context switch operation or a branch takenoperation of a branch instruction for example. In a context switchoperation, the current program counter value is saved in the programstatus word along with other state information about the program beingexecuted (such as condition codes), and a new program counter value isloaded pointing to an instruction of a new program module to beexecuted. A branch taken operation is performed in order to permit theprogram to make decisions or loop within the program by loading theresult of the branch instruction into the program counter 5061.

Typically an instruction fetch unit 5055 is employed to fetchinstructions on behalf of the processor 5026. The fetch unit eitherfetches “next sequential instructions”, target instructions of branchtaken instructions, or first instructions of a program following acontext switch. Modern Instruction fetch units often employ prefetchtechniques to speculatively prefetch instructions based on thelikelihood that the prefetched instructions might be used. For example,a fetch unit may fetch 16 bytes of instruction that includes the nextsequential instruction and additional bytes of further sequentialinstructions.

The fetched instructions are then executed by the processor 5026. In anembodiment, the fetched instruction(s) are passed to a dispatch unit5056 of the fetch unit. The dispatch unit decodes the instruction(s) andforwards information about the decoded instruction(s) to appropriateunits 5057, 5058, 5060. An execution unit 5057 will typically receiveinformation about decoded arithmetic instructions from the instructionfetch unit 5055 and will perform arithmetic operations on operandsaccording to the opcode of the instruction. Operands are provided to theexecution unit 5057 preferably either from memory 5025, architectedregisters 5059 or from an immediate field of the instruction beingexecuted. Results of the execution, when stored, are stored either inmemory 5025, registers 5059 or in other machine hardware (such ascontrol registers, PSW registers and the like).

Virtual addresses are transformed into real addresses using dynamicaddress translation 5062 and, optionally, using access registertranslation 5063.

A processor 5026 typically has one or more units 5057, 5058, 5060 forexecuting the function of the instruction. Referring to FIG. 30A, anexecution unit 5057 may communicate 5071 with architected generalregisters 5059, a decode/dispatch unit 5056, a load store unit 5060, andother 5065 processor units by way of interfacing logic 5071. Anexecution unit 5057 may employ several register circuits 5067, 5068,5069 to hold information that the arithmetic logic unit (ALU) 5066 willoperate on. The ALU performs arithmetic operations such as add,subtract, multiply and divide as well as logical function such as and,or and exclusive-or (XOR), rotate and shift. Preferably the ALU supportsspecialized operations that are design dependent. Other circuits mayprovide other architected facilities 5072 including condition codes andrecovery support logic for example. Typically the result of an ALUoperation is held in an output register circuit 5070 which can forwardthe result to a variety of other processing functions. There are manyarrangements of processor units, the present description is onlyintended to provide a representative understanding of one embodiment.

An ADD instruction for example would be executed in an execution unit5057 having arithmetic and logical functionality while a floating pointinstruction for example would be executed in a floating point executionhaving specialized floating point capability. Preferably, an executionunit operates on operands identified by an instruction by performing anopcode defined function on the operands. For example, an ADD instructionmay be executed by an execution unit 5057 on operands found in tworegisters 5059 identified by register fields of the instruction.

The execution unit 5057 performs the arithmetic addition on two operandsand stores the result in a third operand where the third operand may bea third register or one of the two source registers. The execution unitpreferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capableof performing a variety of logical functions such as Shift, Rotate, And,Or and XOR as well as a variety of algebraic functions including any ofadd, subtract, multiply, divide. Some ALUs 5066 are designed for scalaroperations and some for floating point. Data may be Big Endian (wherethe least significant byte is at the highest byte address) or LittleEndian (where the least significant byte is at the lowest byte address)depending on architecture. The IBM z/Architecture is Big Endian. The IBMPower ISA supports both Big Endian and Little Endian execution modes.Signed fields may be sign and magnitude, 1's complement or 2'scomplement depending on architecture. A 2's complement number isadvantageous in that the ALU does not need to design a subtractcapability since either a negative value or a positive value in 2'scomplement requires only an addition within the ALU. Numbers arecommonly described in shorthand, where a 12 bit field defines an addressof a 4,096 byte block and is commonly described as a 4 Kbyte (Kilo-byte)block, for example.

Referring to FIG. 30B, branch instruction information for executing abranch instruction is typically sent to a branch unit 5058 which oftenemploys a branch prediction algorithm such as a branch history table5082 to predict the outcome of the branch before other conditionaloperations are complete. The target of the current branch instructionwill be fetched and speculatively executed before the conditionaloperations are complete. When the conditional operations are completedthe speculatively executed branch instructions are either completed ordiscarded based on the conditions of the conditional operation and thespeculated outcome. A typical branch instruction may test conditioncodes and branch to a target address if the condition codes meet thebranch requirement of the branch instruction, a target address may becalculated based on several numbers including ones found in registerfields or an immediate field of the instruction for example. The branchunit 5058 may employ an ALU 5074 having a plurality of input registercircuits 5075, 5076, 5077 and an output register circuit 5080. Thebranch unit 5058 may communicate 5081 with general registers 5059,decode dispatch unit 5056 or other circuits 5073, for example.

The execution of a group of instructions can be interrupted for avariety of reasons including a context switch initiated by an operatingsystem, a program exception or error causing a context switch, an I/Ointerruption signal causing a context switch or multi-threading activityof a plurality of programs (in a multi-threaded environment), forexample. Preferably a context switch action saves state informationabout a currently executing program and then loads state informationabout another program being invoked. State information may be saved inhardware registers or in memory for example. State informationpreferably comprises a program counter value pointing to a nextinstruction to be executed, condition codes, memory translationinformation and architected register content. A context switch activitycan be exercised by hardware circuits, application programs, operatingsystem programs or firmware code (microcode, pico-code or licensedinternal code (LIC)) alone or in combination.

A processor accesses operands according to instruction defined methods.The instruction may provide an immediate operand using the value of aportion of the instruction, may provide one or more register fieldsexplicitly pointing to either general purpose registers or specialpurpose registers (floating point registers for example). Theinstruction may utilize implied registers identified by an opcode fieldas operands. The instruction may utilize memory locations for operands.A memory location of an operand may be provided by a register, animmediate field, or a combination of registers and immediate field asexemplified by the z/Architecture long displacement facility wherein theinstruction defines a base register, an index register and an immediatefield (displacement field) that are added together to provide theaddress of the operand in memory for example; or the Power ISAaddressing modes wherein D-Form addresses define a base register and animmediate field (displacement field) that are added together to providethe address of the operand in memory; and wherein X-Form addressesdefine a base register and an index register that are added together toprovide the address of the operand in memory. Location herein typicallyimplies a location in main memory (main storage) unless otherwiseindicated.

Referring to FIG. 30C, a processor accesses storage using a load/storeunit 5060. The load/store unit 5060 may perform a load operation byobtaining the address of the target operand in memory 5053 and loadingthe operand in a register 5059 or another memory 5053 location, or mayperform a store operation by obtaining the address of the target operandin memory 5053 and storing data obtained from a register 5059 or anothermemory 5053 location in the target operand location in memory 5053. Theload/store unit 5060 may be speculative and may access memory in asequence that is out-of-order relative to instruction sequence, howeverthe load/store unit 5060 is to maintain the appearance to programs thatinstructions were executed in order. A load/store unit 5060 maycommunicate 5084 with general registers 5059, decode/dispatch unit 5056,cache/memory interface 5053 or other elements 5083 and comprises variousregister circuits 5086, 5087, 5088 and 5089, ALUs 5085 and control logic5090 to calculate storage addresses and to provide pipeline sequencingto keep operations in-order. Some operations may be out of order but theload/store unit provides functionality to make the out of orderoperations to appear to the program as having been performed in order,as is well known in the art.

Preferably addresses that an application program “sees” are oftenreferred to as virtual addresses. Virtual addresses are sometimesreferred to as “logical addresses” and “effective addresses”. Thesevirtual addresses are virtual in that they are redirected to physicalmemory location by one of a variety of dynamic address translation (DAT)technologies including, but not limited to, simply prefixing a virtualaddress with an offset value, translating the virtual address via one ormore translation tables, the translation tables preferably comprising atleast a segment table and a page table alone or in combination,preferably, the segment table having an entry pointing to the pagetable. In the z/Architecture, a hierarchy of translation is providedincluding a region first table, a region second table, a region thirdtable, a segment table and an optional page table. The performance ofthe address translation is often improved by utilizing a translationlookaside buffer (TLB) which comprises entries mapping a virtual addressto an associated physical memory location. The entries are created whenthe DAT translates a virtual address using the translation tables.Subsequent use of the virtual address can then utilize the entry of thefast TLB rather than the slow sequential translation table accesses. TLBcontent may be managed by a variety of replacement algorithms includingLRU (Least Recently used).

In the case where the processor is a processor of a multi-processorsystem, each processor has responsibility to keep shared resources, suchas I/O, caches, TLBs and memory, interlocked for coherency. Typically,“snoop” technologies will be utilized in maintaining cache coherency. Ina snoop environment, each cache line may be marked as being in any oneof a shared state, an exclusive state, a changed state, an invalid stateand the like in order to facilitate sharing.

I/O units 5054 (FIG. 29) provide the processor with means for attachingto peripheral devices including tape, disc, printers, displays, andnetworks for example. I/O units are often presented to the computerprogram by software drivers. In mainframes, such as the System z fromIBM®, channel adapters and open system adapters are I/O units of themainframe that provide the communications between the operating systemand peripheral devices. In RISC servers, such as Power Systems fromIBM®, proprietary adapters and open system adapters are I/O units thatprovide the communications between the operating system and peripheraldevices.

Further, other types of computing environments can benefit from one ormore aspects. As an example, an environment may include an emulator(e.g., software or other emulation mechanisms), in which a particulararchitecture (including, for instance, instruction execution,architected functions, such as address translation, and architectedregisters) or a subset thereof is emulated (e.g., on a native computersystem having a processor and memory). In such an environment, one ormore emulation functions of the emulator can implement one or moreembodiments, even though a computer executing the emulator may have adifferent architecture than the capabilities being emulated. As oneexample, in emulation mode, the specific instruction or operation beingemulated is decoded, and an appropriate emulation function is built toimplement the individual instruction or operation.

In an emulation environment, a host computer includes, for instance, amemory to store instructions and data; an instruction fetch unit tofetch instructions from memory and to optionally, provide localbuffering for the fetched instruction; an instruction decode unit toreceive the fetched instructions and to determine the type ofinstructions that have been fetched; and an instruction execution unitto execute the instructions. Execution may include loading data into aregister from memory; storing data back to memory from a register; orperforming some type of arithmetic or logical operation, as determinedby the decode unit. In one example, each unit is implemented insoftware. For instance, the operations being performed by the units areimplemented as one or more subroutines within emulator software.

More particularly, in a mainframe, architected machine instructions areused by programmers, usually today “C” programmers, often by way of acompiler application. These instructions stored in the storage mediummay be executed natively in a Power Systems or a z/Architecture IBM®Server, or alternatively in machines executing other architectures. Theycan be emulated in the existing and in future IBM® mainframe servers,Power Systems servers and on other machines of IBM® (e.g., System xServers). They can be executed in machines running Linux on a widevariety of machines using hardware manufactured by IBM®, Intel®, AMD,and others. Besides execution on that hardware under a PowerArchitecture or z/Architecture, Linux can be used as well as machineswhich use emulation by Hercules, UMX, or FSI (Fundamental Software,Inc), where generally execution is in an emulation mode. In emulationmode, emulation software is executed by a native processor to emulatethe architecture of an emulated processor.

The native processor typically executes emulation software comprisingeither firmware or a native operating system to perform emulation of theemulated processor. The emulation software is responsible for fetchingand executing instructions of the emulated processor architecture. Theemulation software maintains an emulated program counter to keep trackof instruction boundaries. The emulation software may fetch one or moreemulated machine instructions at a time and convert the one or moreemulated machine instructions to a corresponding group of native machineinstructions for execution by the native processor. These convertedinstructions may be cached such that a faster conversion can beaccomplished. Notwithstanding, the emulation software is to maintain thearchitecture rules of the emulated processor architecture so as toassure operating systems and applications written for the emulatedprocessor operate correctly. Furthermore, the emulation software is toprovide resources identified by the emulated processor architectureincluding, but not limited to, control registers, general purposeregisters, floating point registers, dynamic address translationfunction including segment tables and page tables for example, interruptmechanisms, context switch mechanisms, Time of Day (TOD) clocks andarchitected interfaces to I/O subsystems such that an operating systemor an application program designed to run on the emulated processor, canbe run on the native processor having the emulation software.

A specific instruction being emulated is decoded, and a subroutine iscalled to perform the function of the individual instruction. Anemulation software function emulating a function of an emulatedprocessor is implemented, for example, in a “C” subroutine or driver, orsome other method of providing a driver for the specific hardware aswill be within the skill of those in the art after understanding thedescription of the preferred embodiment. Various software and hardwareemulation patents including, but not limited to U.S. Pat. No. 5,551,013,entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.;and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored TargetRoutines for Emulating Incompatible Instructions on a Target Processor”,by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding GuestInstruction to Directly Access Emulation Routines that Emulate the GuestInstructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled“Symmetrical Multiprocessing Bus and Chipset Used for CoprocessorSupport Allowing Non-Native Code to Run in a System”, by Gorishek et al;and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object CodeTranslator for Architecture Emulation and Dynamic Optimizing Object CodeTranslation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825,entitled “Method for Emulating Guest Instructions on a Host ComputerThrough Dynamic Recompilation of Host Instructions”, by Eric Traut, eachof which is hereby incorporated herein by reference in its entirety; andmany others, illustrate a variety of known ways to achieve emulation ofan instruction format architected for a different machine for a targetmachine available to those skilled in the art.

In FIG. 31, an example of an emulated host computer system 5092 isprovided that emulates a host computer system 5000′ of a hostarchitecture. In the emulated host computer system 5092, the hostprocessor (CPU) 5091 is an emulated host processor (or virtual hostprocessor) and comprises an emulation processor 5093 having a differentnative instruction set architecture than that of the processor 5091 ofthe host computer 5000′. The emulated host computer system 5092 hasmemory 5094 accessible to the emulation processor 5093. In the exampleembodiment, the memory 5094 is partitioned into a host computer memory5096 portion and an emulation routines 5097 portion. The host computermemory 5096 is available to programs of the emulated host computer 5092according to host computer architecture. The emulation processor 5093executes native instructions of an architected instruction set of anarchitecture other than that of the emulated processor 5091, the nativeinstructions obtained from emulation routines memory 5097, and mayaccess a host instruction for execution from a program in host computermemory 5096 by employing one or more instruction(s) obtained in asequence & access/decode routine which may decode the hostinstruction(s) accessed to determine a native instruction executionroutine for emulating the function of the host instruction accessed.Other facilities that are defined for the host computer system 5000′architecture may be emulated by architected facilities routines,including such facilities as general purpose registers, controlregisters, dynamic address translation and I/O subsystem support andprocessor cache, for example. The emulation routines may also takeadvantage of functions available in the emulation processor 5093 (suchas general registers and dynamic translation of virtual addresses) toimprove performance of the emulation routines. Special hardware andoff-load engines may also be provided to assist the processor 5093 inemulating the function of the host computer 5000′.

In a further embodiment, one or more aspects relate to cloud computing.It is understood in advance that although this disclosure includes adetailed description on cloud computing, implementation of the teachingsrecited herein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g. networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based email). Theconsumer does not manage or control the underlying cloud infrastructureincluding network, servers, operating systems, storage, or evenindividual application capabilities, with the possible exception oflimited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as Follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forloadbalancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure comprising anetwork of interconnected nodes.

Referring now to FIG. 32, a schematic of an example of a cloud computingnode is shown. Cloud computing node 6010 is only one example of asuitable cloud computing node and is not intended to suggest anylimitation as to the scope of use or functionality of embodiments of theinvention described herein. Regardless, cloud computing node 6010 iscapable of being implemented and/or performing any of the functionalityset forth hereinabove.

In cloud computing node 6010 there is a computer system/server 6012,which is operational with numerous other general purpose or specialpurpose computing system environments or configurations. Examples ofwell-known computing systems, environments, and/or configurations thatmay be suitable for use with computer system/server 6012 include, butare not limited to, personal computer systems, server computer systems,thin clients, thick clients, handheld or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 6012 may be described in the general context ofcomputer system executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 6012 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 32, computer system/server 6012 in cloud computing node6010 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 6012 may include, but are notlimited to, one or more processors or processing units 6016, a systemmemory 6028, and a bus 6018 that couples various system componentsincluding system memory 6028 to processor 6016.

Bus 6018 represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnect (PCI) bus.

Computer system/server 6012 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 6012, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 6028 can include computer system readable media in theform of volatile memory, such as random access memory (RAM) 6030 and/orcache memory 6032. Computer system/server 6012 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 6034 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 6018 by one or more datamedia interfaces. As will be further depicted and described below,memory 6028 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 6040, having a set (at least one) of program modules6042, may be stored in memory 6028 by way of example, and notlimitation, as well as an operating system, one or more applicationprograms, other program modules, and program data. Each of the operatingsystem, one or more application programs, other program modules, andprogram data or some combination thereof, may include an implementationof a networking environment. Program modules 6042 generally carry outthe functions and/or methodologies of embodiments of the invention asdescribed herein.

Computer system/server 6012 may also communicate with one or moreexternal devices 6014 such as a keyboard, a pointing device, a display6024, etc.; one or more devices that enable a user to interact withcomputer system/server 6012; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 6012 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 6022. Still yet, computer system/server6012 can communicate with one or more networks such as a local areanetwork (LAN), a general wide area network (WAN), and/or a publicnetwork (e.g., the Internet) via network adapter 6020. As depicted,network adapter 6020 communicates with the other components of computersystem/server 6012 via bus 6018. It should be understood that althoughnot shown, other hardware and/or software components could be used inconjunction with computer system/server 6012. Examples, include, but arenot limited to: microcode, device drivers, redundant processing units,external disk drive arrays, RAID systems, tape drives, and data archivalstorage systems, etc.

Referring now to FIG. 33, illustrative cloud computing environment 6050is depicted. As shown, cloud computing environment 6050 comprises one ormore cloud computing nodes 6010 with which local computing devices usedby cloud consumers, such as, for example, personal digital assistant(PDA) or cellular telephone 6054A, desktop computer 6054B, laptopcomputer 6054C, and/or automobile computer system 6054N may communicate.Nodes 6010 may communicate with one another. They may be grouped (notshown) physically or virtually, in one or more networks, such asPrivate, Community, Public, or Hybrid clouds as described hereinabove,or a combination thereof. This allows cloud computing environment 6050to offer infrastructure, platforms and/or software as services for whicha cloud consumer does not need to maintain resources on a localcomputing device. It is understood that the types of computing devices6054A-N shown in FIG. 33 are intended to be illustrative only and thatcomputing nodes 6010 and cloud computing environment 6050 cancommunicate with any type of computerized device over any type ofnetwork and/or network addressable connection (e.g., using a webbrowser).

Referring now to FIG. 34, a set of functional abstraction layersprovided by cloud computing environment 6050 (FIG. 33) is shown. Itshould be understood in advance that the components, layers, andfunctions shown in FIG. 34 are intended to be illustrative only andembodiments of the invention are not limited thereto. As depicted, thefollowing layers and corresponding functions are provided:

Hardware and software layer 6060 includes hardware and softwarecomponents. Examples of hardware components include mainframes, in oneexample IBM® zSeries® systems; RISC (Reduced Instruction Set Computer)architecture based servers, in one example IBM pSeries® systems; IBMxSeries® systems; IBM BladeCenter® systems; storage devices; networksand networking components. Examples of software components includenetwork application server software, in one example IBM WebSphere®application server software; and database software, in one example IBMDB2® database software. (IBM, zSeries, pSeries, xSeries, BladeCenter,WebSphere, and DB2 are trademarks of International Business MachinesCorporation registered in many jurisdictions worldwide).

Virtualization layer 6062 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers;virtual storage; virtual networks, including virtual private networks;virtual applications and operating systems; and virtual clients.

In one example, management layer 6064 may provide the functionsdescribed below. Resource provisioning provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricingprovide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal provides access to the cloud computing environment forconsumers and system administrators. Service level management providescloud computing resource allocation and management such that requiredservice levels are met. Service Level Agreement (SLA) planning andfulfillment provide pre-arrangement for, and procurement of, cloudcomputing resources for which a future requirement is anticipated inaccordance with an SLA.

Workloads layer 6066 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation; software development and lifecycle management; virtualclassroom education delivery; data analytics processing; and transactionprocessing.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising”,when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components and/or groups thereof

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of one or more embodiments has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theembodiment was chosen and described in order to best explain variousaspects and the practical application, and to enable others of ordinaryskill in the art to understand various embodiments with variousmodifications as are suited to the particular use contemplated.

1. A computer program product for managing migration of partitions, saidcomputer program product comprising: a computer readable storage mediumreadable by a processing circuit and storing instructions for executionby the processing circuit for performing a method comprising: obtaining,by an optimizer executing in a processor, an indication that a partitionexecuting an application using one or more extended mode features is tobe migrated to a system in which at least one extended mode feature ofthe one or more extended features is unsupported; and removing, based onobtaining the indication, at least a portion of code of the applicationto facilitate migration of the partition to the system in which at leastone extended mode feature is unsupported.
 2. The computer programproduct of claim 1, wherein the one or more extended mode featurescomprise a feature at an instruction set level different from aninstruction set level of the application.
 3. The computer programproduct of claim 1, wherein the application comprises optimized code,the optimized code including the one or more extended mode features, andwherein the removing comprises removing the optimized code.
 4. Thecomputer program product of claim 1, wherein the application comprisesoptimized code, the optimized code including the one or more extendedmode features, and wherein the removing comprises removing a portion ofthe optimized code, the portion of the optimized code being unsupportedby the system.
 5. The computer program product of claim 1, wherein themethod further comprises reporting completion of the removing the atleast a portion of the code, and based on reporting within a predefinedtime window, migration of the partition continues.
 6. The computerprogram product of claim 1, wherein the obtaining comprises obtainingthe indication from a component of the computing environment, and basedon the component determining the optimizer has not reported completionof the removing the at least a portion of the code within a predefinedtime window, the application is cancelled or terminated.
 7. The computerprogram product of claim 1, wherein the removing comprises: determiningwhether the application is currently executing optimized code of theapplication or unoptimized code of the application; and based ondetermining the application is currently executing unoptimized code ofthe application: removing the at least a portion of the code; andreporting that the at least a portion of the code has been removed,wherein the application continues to execute.
 8. The computer programproduct of claim 1, wherein the removing comprises: determining whetherthe application is currently executing optimized code of the applicationor unoptimized code of the application; based on determining theapplication is currently executing optimized code of the application:checking whether the optimized code is currently executing code that issupported by the system to which the partition is being migrated; andbased on the checking indicating the optimized code is currentlyexecuting code that is supported by the system, removing the at least aportion of the code, and reporting that the at least a portion of thecode is removed, wherein the application continues to execute.
 9. Thecomputer program product of claim 1, wherein the removing comprises:determining whether the application is currently executing optimizedcode of the application or unoptimized code of the application; andbased on determining the application is currently executing optimizedcode of the application: checking whether the optimized code iscurrently executing code that is unsupported by the system to which thepartition is being migrated; and based on the checking indicating theoptimized code is currently executing code that is unsupported by thesystem, obtaining state of the unoptimized code, and based on obtainingthe state, removing the at least a portion of the code.
 10. The computerprogram product of claim 9, wherein the application continues executingbased on the obtained state.
 11. A computer system for managingmigration of partitions, said computer system comprising: a memory; anda processor in communications with the memory, wherein the computersystem is configured to perform a method, said method comprising:obtaining, by an optimizer executing in the processor, an indicationthat a partition executing an application using one or more extendedmode features is to be migrated to a system in which at least oneextended mode feature of the one or more extended features isunsupported; and removing, based on obtaining the indication, at least aportion of code of the application to facilitate migration of thepartition to the system in which at least one extended mode feature isunsupported.
 12. The computer system of claim 11, wherein theapplication comprises optimized code, the optimized code including theone or more extended mode features, and wherein the removing comprisesremoving the optimized code.
 13. The computer system of claim 11,wherein the application comprises optimized code, the optimized codeincluding the one or more extended mode features, and wherein theremoving comprises removing a portion of the optimized code, the portionof the optimized code being unsupported by the system.
 14. The computersystem of claim 11, wherein the obtaining comprises obtaining theindication from a component of the computing environment, and based onthe component determining the optimizer has not reported completion ofthe removing the at least a portion of the code within a predefined timewindow, the application is cancelled or terminated.
 15. The computersystem of claim 11, wherein the removing comprises: determining whetherthe application is currently executing optimized code of the applicationor unoptimized code of the application; and based on determining theapplication is currently executing unoptimized code of the application:removing the at least a portion of the code; and reporting that the atleast a portion of the code has been removed, wherein the applicationcontinues to execute.
 16. The computer system of claim 11, wherein theremoving comprises: determining whether the application is currentlyexecuting optimized code of the application or unoptimized code of theapplication; and based on determining the application is currentlyexecuting optimized code of the application: checking whether theoptimized code is currently executing code that is supported by thesystem to which the partition is being migrated; and based on thechecking indicating the optimized code is currently executing code thatis supported by the system, removing the at least a portion of the code,and reporting that the at least a portion of the code is removed,wherein the application continues to execute.
 17. The computer system ofclaim 11, wherein the removing comprises: determining whether theapplication is currently executing optimized code of the application orunoptimized code of the application; and based on determining theapplication is currently executing optimized code of the application:checking whether the optimized code is currently executing code that isunsupported by the system to which the partition is being migrated; andbased on the checking indicating the optimized code is currentlyexecuting code that is unsupported by the system, obtaining state of theunoptimized code, and based on obtaining the state, removing the atleast a portion of the code.